What is the difference between px dip dp and sp

Question

What is the difference between Android units of measure    px dip dp sp

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Screen size in Android is grouped into categories ldpi  mdpi  hdpi  xhdpi  xxhdpi and xxxhdpi  Screen density is the amount of pixels within an area  like inch  of the screen  Generally it is measured in dots-per-inch  dpi    PX Pixels      our usual standard pixel which maps to the screen pixel  px is meant for absolute pixels  This is used if you want to give in terms of absolute pixels for width or height  Not recommended    DP DIP Density pixels   Density independent pixels     dip    dp  In earlier Android versions dip was used and later changed to dp  This is alternative of px  Generally we never use px because it is absolute value  If you use px to set width or height  and if that application is being downloaded into different screen sized devices  then that view will not stretch as per the screen original size  dp is highly recommended to use in place of px  Use dp if you want to mention width and height to grow  amp  shrink dynamically  based on screen sizes  if we give dp dip  android will automatically calculate the pixel size on the basis of 160 pixel sized screen    SP Scale independent pixels      scaled based on user   s font size preference  Fonts should use sp  when mentioning the font sizes to fit for various screen sizes  use sp  This is similar to dp Use sp especially for font sizes to grow  amp  shrink dynamically based on screen sizes   Android Documentation says      when specifying dimensions  always use either dp or sp units  A dp is   a density-independent pixel that corresponds to the physical size of a   pixel at 160 dpi  An sp is the same base unit  but is scaled by the   user s preferred text size  it   s a scale-independent pixel   so you   should use this measurement unit when defining text size

User · Answer

Here s the formula used by Android      px   dp    dpi   160    Where dpi is one of the following screen densities  For a list of all possible densities go here  It defines the  DENSITY    constants    ldpi  low   120dpi  mdpi  medium   160dpi  hdpi  high   240dpi  xhdpi  extra-high   320dpi  xxhdpi  extra-extra-high   480dpi  xxxhdpi  extra-extra-extra-high   640dpi   Taken from here    This will sort out a lot of the confusion when translating between px and dp  if you know your screen dpi   So  let s say you want an image of 60 dp for an hdpi screen then the physical pixel size of 60 dp is   px   60    240   160

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Pixel density  Screen pixel density and resolution vary depending on the platform  Device-independent pixels and scalable pixels are units that provide a flexible way to accommodate a design across platforms   Calculating pixel density  The number of pixels that fit into an inch is referred to as pixel density  High-density screens have more pixels per inch than low-density ones      The number of pixels that fit into an inch is referred to as pixel density  High-density screens have more pixels per inch than low-density ones  As a result  UI elements of the same pixel dimensions appear larger on low-density screens  and smaller on high-density screens   To calculate screen density  you can use this equation   Screen density   Screen width  or height  in pixels   Screen width  or height  in inches    Density independence  Screen pixel density and resolution vary depending on the platform  Device-independent pixels and scalable pixels are units that provide a flexible way to accommodate a design across platforms   Calculating pixel density The number of pixels that fit into an inch is referred to as pixel density  High-density screens have more pixels per inch than low-density ones      Density independence refers to the uniform display of UI elements on screens with different densities   Density-independent pixels  written as dp  pronounced    dips      are flexible units that scale to have uniform dimensions on any screen  Material UIs use density-independent pixels to display elements consistently on screens with different densities      Low-density screen displayed with density independence  High-density screen displayed with density independence   Read full text https   material io design layout pixel-density html

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Difference between dp and sp units mentioned as  user s font size preference  by the answers copied from official documentation can be seen at run time by changing Settings- gt Accessibility- gt Large Text option   Large Text option forces text to become 1 3 times bigger   private static final float LARGE FONT SCALE   1 3f    This might be well of course vendor dependent since it lies in packages apps Settings

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I want to provide an easy way to understand dp  In fact  I think dp is the easiest one to understand  dp is just a physical length unit  It s of the same dimension as mm or inch  It s just convenient for us to write 50dp  60dp rather than 50 160 inch or 60 160 inch  because one dp is just 1 160 inch whatever the screen size or resolution is    The only problem is that  the android dpi of some screens are not accurate  For example  a screen classified to 160dpi may have 170dpi indeed  So the computation result of dp is fuzzy  It should be approximately the same as 1 160 inch

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I ve come across a good article about designing Android apps UI for different screen resolutions  and I d like to leave it here just for somebody searching in this area  Yes  I know that it s somehow described in Google docs  and mentioned in the posts above   I read that but it was not good for me  yeah  I may be too stupid    It remained unclear for me how to design layouts capable to handle different screen size  I hate DP concept and so on  when I need to implement a  flexible  UI layout for different screens   Hey iOS developers - yes  you re right it s Storyboard concept    Android has not bad UI concept  but lacks iOS Storyboard features  unfortunately  Designing flexible UI in Android is not easy thing  at the best    Here goes the article that helped me to understand what to do in Android to make layouts for different screen sizes    JMSTUDIO Blog  - Decide Android App Screen Size      How to Design UI for Android Apps for Different Screen Size       To design an app UI for different screen sizes  our initial design has to   meet a minimum required space for each screen size  Android defines a   minimum size  in dp  for each generalized screen type  Here is an   Android screen size guideline       When we get the screen size in dp  it is not enough for us to design   the Android app UI  For each screen size  we need to prepare graphics   and bitmap images for each density  Here is an Android screen density   guideline          For easy calculation  we can follow the 3 4 6 8 scaling ratio between   the four generalized densities  If we create a 36  36 pixel picture for   ldpi device  the rest densities pictures size will be 48  48 for mdpi    72  72 for hdpi  and 96  96 for xhdpi       How to Design Android Apps UI in Photoshop      Many designers have problems for designing Android app UI in photoshop or other pixel   based graphic design tools because of density-independent unit  dp    Designers don   t know how to map dp to pixel  Google also doesn   t give   a clear Android UI design guide for them  though they give a basic   formula for dp and pixel translation       As Android   s definition  1pd equal to 1px under 160 dpi device  mdpi     So we want to design an Android app for xlarge Android device with   mdpi density  we can define our UI size in pixel as 960 pixel in width   and 720px in height  Follow the same mapping rule  we can get   following Android App screen size UI design guideline          ADDED  If you interested in  flexible  UI too  have a look at this library  An Android SDK that provides a new size unit - sdp  scalable dp   This size unit scales with the screen size  this also mentioned in an answer here  about SDP library   ADDED2 Google has finally understood usefulness of iOS Storeboard UI concept  and here goes ConstraintLayout for Android world  Build a Responsive UI with ConstraintLayout

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sp   scale independent pixel dp   dip   density independent pixels dpi   dots per inch  We should avoid to use sp  We should use dp to support multiple screens   Android supports different screen resolutions  ldpi  low   120  dpi mdpi  medium   160  dpi hdpi  high   240  dpi xhdpi  extra-high   320  dpi xxhdpi  extra-extra-high   480  dpi xxxhdpi  extra-extra-extra-high   640  dpi  An 120 dp ldpi device has 120 pixels in 1 inch size  The same for other densities    We as software engineers should use this conversion formula   pixel   dp    density   160   So 240 dpi device s 1 dp will have   1    240 160    3 2   1 5 pixels  And 480 dpi device s 1 dp will have   1    480 160    3 pixels  Using this 1 5 and 3 pixels knowledge  a software engineer can design layouts for different densities  To check screen parameters of any device  DisplayMetrics metrics   new DisplayMetrics    getWindowManager   getDefaultDisplay   getMetrics metrics    Toast makeText      this       quot 4  quot    metrics heightPixels    quot   quot    metrics density    quot   quot        metrics densityDpi  Toast LENGTH LONG  show

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Pixels px      corresponds to actual pixels on the screen  This is used if you want to give in terms of absolute pixels for width or height   Density-independent Pixels  dp or dip      an abstract unit that is based on the physical density of the screen  These units are relative to a 160 dpi screen  so one dp is one pixel on a 160 dpi screen  The ratio of dp-to-pixel will change with the screen density  but not necessarily in direct proportion  Note  The compiler accepts both    dip    and    dp     though    dp    is more consistent with    sp      Scale-independent Pixels sp      this is like the dp unit  but it is also scaled by the user   s font size preference  It is recommend you use this unit when specifying font sizes  so they will be adjusted for both the screen density and user   s preference   Always use dp and sp only  sp for font sizes and dp for everything else  It will make UI compatible for Android devices with different densities   You can learn more about pixel and dp from   https   www google com design spec layout units-measurements html units-measurements-density-independent-pixels-dp-  Source url - http   www androidtutorialshub com what-is-the-difference-between-px-dp-dip-sp-on-android

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Definitions  px or dot is a pixel on the physical screen   dpi are pixels per inch on the physical screen and represent the density of the display   Android gives alias names to several densities   ldpi  low   120dpi mdpi  medium   160dpi hdpi  high   240dpi   most devices in 2015 are here  xhdpi  extra-high   320dpi   Apple iPhone 4 5 6  Nexus 4  xxhdpi  extra-extra-high   480dpi   Nexus 5  xxxhdpi  extra-extra-extra-high   640dpi   dip or dp are density-indenpendant pixels  i e  they correspond to more or less pixels depending on the physical density    1dp   1px on mdpi     sp or sip is a scale-independant pixel  They are scaled when the Large Text option is turned on in Settings   Accessibility   1sp   1dp 1sp   1 2dp with accessibility Large Text   What to use      Use sp for Text size       Use dp for everything else

User · Answer

You can see the difference between px and dp from the below picture  and you can also find that the px and dp could not guarantee the same physical sizes on the different screens

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From the Android Developer Documentation     px  gt  Pixels - corresponds to actual pixels on the screen      in  gt  Inches - based on the physical size of the screen   gt  1 Inch   2 54 centimeters     mm  gt  Millimeters - based on the physical size of the screen      pt  gt  Points - 1 72 of an inch based on the physical size of the screen      dp or dip  gt  Density-independent Pixels - an abstract unit that is based on the physical density of the screen  These units are relative to a 160 dpi screen  so one dp is one pixel on a 160 dpi screen  The ratio of dp-to-pixel will change with the screen density  but not necessarily in direct proportion  Note  The compiler accepts both  quot dip quot  and  quot dp quot   though  quot dp quot  is more consistent with  quot sp quot       sp  gt  Scaleable Pixels OR scale-independent pixels - this is like the dp unit  but it is also scaled by the user s font size preference  It is recommended you use this unit when specifying font sizes  so they will be adjusted for both the screen density and user s preference  Note  the Android documentation is inconsistent on what sp actually stands for  one doc says  quot scale-independent pixels quot   the other says  quot scaleable pixels quot      From Understanding Density Independence In Android      Density Bucket Screen Density Physical Size Pixel Size     ldpi 120 dpi 0 5 x 0 5 in 0 5 in   120 dpi   60x60 px   mdpi 160 dpi 0 5 x 0 5 in 0 5 in   160 dpi   80x80 px   hdpi 240 dpi 0 5 x 0 5 in 0 5 in   240 dpi   120x120 px   xhdpi 320 dpi 0 5 x 0 5 in 0 5 in   320 dpi   160x160 px   xxhdpi 480 dpi 0 5 x 0 5 in 0 5 in   480 dpi   240x240 px   xxxhdpi 640 dpi 0 5 x 0 5 in 0 5 in   640 dpi   320x320 px        Unit Description Units Per Physical Inch Density Independent  Same Physical Size On Every Screen      px Pixels Varies No No   in Inches 1 Yes Yes   mm Millimeters 25 4 Yes Yes   pt Points 72 Yes Yes   dp Density Independent Pixels  160 Yes No   sp Scale Independent Pixels  160 Yes No     More info can be also be found in the Google Design Documentation

User · Answer

I have calculated the formula below to make the conversions dpi to dp and sp

User · Answer

SDP - a scalable size unit - basically it is not a unit  but dimension resources for different screen size   Try the sdp library from Intuit  It s very handy to solve unit problems  and you can quickly support multiple screens   Usage  android paddingBottom   dimen  15sdp  for positive and android layout marginTop   dimen  minus10sdp   for negative sdp sdp  It has equivalent value in dp for each size in values-sw lt N gt dp folders  sw   smallestWidth    Attention  Use it carefully  In most cases you still need to design a different layout for tablets   Example   lt LinearLayout           android layout width  wrap content            android layout height  wrap content            android layout marginTop   dimen  minus10sdp            android paddingBottom   dimen  15sdp            android orientation  horizontal   gt                    lt TextView                     android layout width  wrap content                      android layout height  wrap content                      android includeFontPadding  false                      android text                         android textColor   ED6C27                      android textSize   dimen  70sdp                      android textStyle  bold    gt                    lt TextView                     android layout width  wrap content                      android layout height  wrap content                      android includeFontPadding  false                      android text  U                      android textColor   android color black                      android textSize   dimen  70sdp    gt               lt  LinearLayout gt    You can use db for text size  but I prefer ssp for text size   For more details  check the library GitHub page

User · Answer

I would only use dp   There is a lot of talk about using  sp  for font sizes  and while I appreciate the point  I don t think that it is the right thing to do from a design point of view  You can end up breaking your design if the user has some wonky font size selection  and the user will end up blaming the app  and not their own life choices   Also  if you take an sp-font app on a 160 nbsp dpi tablet  you will find that everything scales up    but your font  which is going to look tiny in comparison  It isn t a good look   While the idea of  sp  fonts has a good heart  it is a poor idea  Stick with dp for everything

User · Answer

The ratio of dp-to-pixel will change with the screen density  but not necessarily in direct proportion   Note  The compiler accepts both  dip  and  dp   though  dp  is more consistent with  sp    Scale-independent Pixels - this is like the dp unit  but it is also scaled by the user s font size preference

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Please read the answer from community wiki  Below mentioned are some information to be considered in addition to the above answers  Most Android developers miss this while developing apps  so I am adding these points   sp   scale independent pixel  dp   density independent pixels  dpi   density pixels  I have gone through the above answers   not finding them exactly correct  sp for text size  dp for layout bounds - standard  But sp for text size will break the layout if used carelessly in most of the devices    sp take the textsize of the device  whereas dp take that of device density standard  never change in a device  Say 100sp text can occupies 80  of screen or 100  of screen depending on the font size set in device    You can use sp for layout bounds also  it will work    No standard app use sp for whole text  Use sp and dp for text size considering UX    Dont use sp for text in toolbar  can use android dimens available for different screen sizes with dp  Dont use sp for text in small bounded buttons  very smaller text  etc   Some people use huge FONT size in their phone for more readability  giving them small hardcoded sized text will be an UX issue  Put sp for text where necessary  but make sure it won t break the layout when user changes his settings   Similarly if you have a single app supporting all dimensions  adding xxxhdpi assets increases the app size a lot  But now xxxhdpi phones are common so we have to include xxxhdpi assets atleast for icons in side bar  toolbar and bottom bar  Its better to move to vector images to have a uniform and better quality images for all screen sizes   Also note that people use custom font in their phone  So lack of a font can cause problems regarding spacing and all  Say text size 12sp for a custom font may take some pixels extra than default font   Refer google developer site for screendensities and basedensity details for android  https   developer android com training multiscreen screendensities

User · Answer

Screen Size in Android is grouped into categories small  medium  large  extra large  double-extra and triple-extra  Screen density is the amount of pixels within an area  like inch  of the screen  Generally it is measured in dots-per-inch  dpi   Screen density is grouped as low  medium  high and extra high  Resolution is the total number of pixels in the screen    dp  Density Independent Pixel  it varies based on screen density   In 160 dpi screen  1 dp   1 pixel  Except for font size  use dp always  dip  dip    dp  In earlier Android versions dip was used and later changed to dp  sp  Scale Independent Pixel  scaled based on user   s font size preference  Fonts should use sp  px  our usual standard pixel which maps to the screen pixel  in  inches  with respect to the physical screen size  mm  millimeters  with respect to the physical screen size  pt  1 72 of an inch  with respect to the physical screen size    Formula for Conversion between Units   px   dp    dpi   160    dp to px in device  Following example may help understand better  The scaling occurs based on bucket size of 120 ldpi   160 mdpi   240 hdpi   320 xhdpi   480 xxhdpi  and 640 xxxhdpi   The Google suggested ratio for designing is 3 4 6 8 12 for ldpi mdpi hdpi xhdpi xxhdpi  A 150px X 150px image will occupy         150 dp X 150 dp screen space in mdpi   100 dp X 100 dp screen space in hdpi   75 dp X 75 dp screen space in xhdpi      You may use the following DPI calculator to fix your image sizes and other dimensions when you wish to have an uniform UI design in all Android devices   DPI Calculator in Java     Program output LDPI  165 0 X 60 0 MDPI  220 0 X 80 0 HDPI  330 0 X 120 0 XHDPI  440 0 X 160 0 XXHDPI  660 0 X 240 0 XXXHDPI  880 0 X 320 0      public class DPICalculator    private final float LDPI   120  private final float MDPI   160  private final float HDPI   240  private final float XHDPI   320  private final float XXHDPI   480  private final float XXXHDPI   640       private float forDeviceDensity  private float width  private float height   public DPICalculator float forDeviceDensity  float width  float height       this forDeviceDensity   forDeviceDensity      this width   width      this height   height     public static void main String    args        DPICalculator dpiCalculator   new DPICalculator 240 330 120       dpiCalculator calculateDPI        private float getPx float dp  float value        float px   dp    value   forDeviceDensity                return px     private void calculateDPI          float ldpiW   getPx LDPI width               float ldpiH    getPx LDPI height       float mdpiW   getPx MDPI width               float mdpiH    getPx MDPI height               float hdpiW   getPx HDPI width               float hdpiH    getPx HDPI height              float xdpiW   getPx XHDPI width               float xdpiH    getPx XHDPI height       float xxdpiW   getPx XXHDPI width               float xxdpiH    getPx XXHDPI height       float xxxdpiW   getPx XXXHDPI width               float xxxdpiH    getPx XXXHDPI height        System out println  LDPI      ldpiW     X     ldpiH       System out println  MDPI      mdpiW     X     mdpiH       System out println  HDPI      hdpiW     X     hdpiH       System out println  XHDPI      xdpiW     X     xdpiH       System out println  XXHDPI      xxdpiW     X     xxdpiH       System out println  XXXHDPI      xxxdpiW     X     xxxdpiH                    More Information refer following link   http   javapapers com android difference-between-dp-dip-sp-px-in-mm-pt-in-android

User · Answer

px  Pixels - corresponds to actual pixels on the screen   dp or dip  Density-independent Pixels - an abstract unit that is based on the physical density of the screen  These units are relative to a 160 dpi screen  so one dp is one pixel on a 160 dpi screen   Use of dp   Density independence - Your application achieves    density independence    when it preserves the physical size  from the user   s point of view  of user interface elements when displayed on screens with different densities   ie  The image should look the same size  not enlarged or shrinked  in different types of screens   sp  Scale-independent Pixels - this is like the dp unit  but it is also scaled by the user s font size preference   http   developer android com guide topics resources more-resources html Dimension

User · Answer

px - one pixel  same as to what is used in CSS  JavaScript  etc  sp - scale-independent pixels dip - density-independent pixels   Normally sp is used for font sizes  while dip is used  also called dp  for others

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dpi -   Dots per inches Measuring the pixel density of the screen    px - pixel   For mapping screen pixels   pt - points   About 1 72 of an inch  with respect to physical screen size    in - inch  - with respect to physical screen size 1 inch   2 54 cm    mm- milimeter  - with respect to physical screen size   sp - scale-independent pixel    Based on user s font size preference  Font should be in  sp     dip -   dip    dp Density independent pixel  It varies based on Screen Density  In 160 dpi screen  1 dp   1 pixel  Use dp except the text font size    In standard  dp and sp are used  sp for font size and dp for everything else   Formula for conversion of units      px   dp     dpi   160      Density Bucket - gt  Screen Display   gt  Physical Size          gt  Pixel Size                     ldpi         - gt  120 dpi            gt  0 5 x 0 5 in           gt  0 5 in   120 dpi   60x60 px     mdpi         - gt  160 dpi            gt  0 5 x 0 5 in           gt  0 5 in   160 dpi   80x80 px     hdpi         - gt  240 dpi            gt  0 5 x 0 5 in           gt  0 5 in   240 dpi   120x120 px    xhdpi        - gt  320 dpi            gt  0 5 x 0 5 in           gt  0 5 in   320 dpi   160x160 px    xxhdpi       - gt  480 dpi            gt  0 5 x 0 5 in           gt  0 5 in   480 dpi   240x240 px   xxxhdpi      - gt  640 dpi            gt  0 5 x 0 5 in           gt  0 5 in   640 dpi   320x320 px

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Pretty much everything about this and how to achieve the best support for multiple screens of different sizes and densities is very well documented here    Supporting Multiple Screens      Screen size   Actual physical size  measured as the screen s diagonal    For simplicity  Android groups all actual screen sizes into four   generalized sizes  small  normal  large  and extra-large       Screen density    The number of pixels within a physical area of the   screen  usually referred to as dpi  dots per inch   For example  a    low  density screen has fewer pixels within a given physical area    compared to a  normal  or  high  density screen  For simplicity    Android groups all actual screen densities into six generalized   densities  low  medium  high  extra-high  extra-extra-high  and   extra-extra-extra-high       OrientationThe orientation of the screen from the user s point of   view  This is either landscape or portrait  meaning that the screen s   aspect ratio is either wide or tall  respectively  Be aware that not   only do different devices operate in different orientations by   default  but the orientation can change at runtime when the user   rotates the device        Resolution The total number of physical pixels on   a screen  When adding support for multiple screens  applications do   not work directly with resolution  applications should be concerned   only with screen size and density  as specified by the generalized   size and density groups        Density-independent pixel  dp  A virtual   pixel unit that you should use when defining UI layout  to express   layout dimensions or position in a density-independent way     The density-independent pixel is equivalent to one physical pixel on a 160   dpi screen  which is the baseline density assumed by the system for a    medium  density screen  At runtime  the system transparently handles   any scaling of the dp units  as necessary  based on the actual density   of the screen in use  The conversion of dp units to screen pixels is   simple     px   dp    dpi   160      For example  on a 240 dpi screen  1 dp   equals 1 5 physical pixels  You should always use dp units when   defining your application s UI  to ensure proper display of your UI on   screens with different densities    If you are any serious about developing an Android app for more than one type of device  you should have read the screens support development document at least once  In addition to that  it is always a good thing to know the actual number of active devices that have a particular screen configuration    Screen Sizes and Densities

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Source 1  Source 2  Source 3   data from source 3 is given below      These are dimension values defined in XML  A dimension is specified   with a number followed by a unit of measure  For example  10px  2in    5sp  The following units of measure are supported by Android       dp      Density-independent Pixels - An abstract unit that is based on the   physical density of the screen  These units are relative to a 160 dpi    dots per inch  screen  on which 1dp is roughly equal to 1px  When   running on a higher density screen  the number of pixels used to draw   1dp is scaled up by a factor appropriate for the screen s dpi    Likewise  when on a lower density screen  the number of pixels used   for 1dp is scaled down  The ratio of dp-to-pixel will change with the   screen density  but not necessarily in direct proportion  Using dp   units  instead of px units  is a simple solution to making the view   dimensions in your layout resize properly for different screen   densities  In other words  it provides consistency for the real-world   sizes of your UI elements across different devices       sp      Scale-independent Pixels - This is like the dp unit  but it is also   scaled by the user s font size preference  It is recommended that you use   this unit when specifying font sizes  so they will be adjusted for   both the screen density and the user s preference       pt      Points - 1 72 of an inch based on the physical size of the screen       px      Pixels - Corresponds to actual pixels on the screen  This unit of   measure is not recommended because the actual representation can vary   across devices  each devices may have a different number of pixels per   inch and may have more or fewer total pixels available on the screen       mm      Millimeters - Based on the physical size of the screen       in      Inches - Based on the physical size of the screen    Note  A dimension is a simple resource that is referenced using the value provided in the name attribute  not the name of the XML file   As such  you can combine dimension resources with other simple resources in the one XML file  under one  element

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1  dp   density independent pixels   The number of pixels represented in one unit of dp will increase as the screen resolution increases  when you have more dots pixels per inch   Conversely on devices with lower resolution  the number of pixels represented in on unit of dp will decrease  Since this is a relative unit  it needs to have a baseline to be compared with  This baseline is a 160 dpi screen  This is the equation  px   dp    dpi   160     2  sp   scale independent pixels   This unit scales according to the screen dpi  similar to dp  as well as the user   s font size preference    3  px   pixels    Actual pixels or dots on the screen     For more details you can visit      Android Developer Guide   Dimension   Android Developer Guide   Screens

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px - Pixels - point per scale corresponds to actual pixels on the screen  i - Inches - based on the physical size of the screen  mm - Millimeters - based on the physical size of the screen  pt - Points - 1 72 of an inch based on the physical size of the screen  dp - Density-independent Pixels - an abstract unit that is based on the physical density of the screen  These units are relative to a 160 dpi screen  so one dp is one pixel on a 160 dpi screen  The ratio of dp-to-pixel will change with the screen density  but not necessarily in direct proportion  Note  The compiler accepts both dip and dp  though dp is more consistent with sp  sp - scalable pixels - this is like the dp unit  but it is also scaled by the user s font size preference  It is recommended that you use this unit when specifying font sizes  so they will be adjusted for both the screen density and user s preference  Take the example of two screens that are the same size but one has a screen density of 160 dpi  dots per inch  i e  pixels per inch  and the other is 240 dpi                            Lower resolution screen     Higher resolution  same size Physical Width                      1 5 inches                        1 5 inches Dots Per Inch     dpi                   160                               240 Pixels   width dpi                  240                               360 Density  factor of baseline 160     1 0                               1 5  Density-independent pixels          240                               240     dip    or    dp    or    dps      Scale-independent pixels       sip    or    sp                      Depends on user font size settings    same

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sp  scale independent pixel   You should use it with texts because it is automatically scaled according to the font size that is being used by the user in his device      px  pixel or picture element is the single point on the screen

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Basically the only time where px applies is one px  and that s if you want exactly one pixel on the screen like in the case of a divider    On  160 dpi  you may get 2-3 pixels    On  120 dpi  it rounds to 0

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The screen of a mobile phone is made up of thousands of tiny dots known as pixels  px   A pixel is the smallest element which goes to make the picture  The more the number of pixels to make a picture or wording  the sharper it becomes and makes the smartphone screen more easily readable   Screen resolution is measured in terms of number of pixels on the screen  Screen resolution is a commonly-used specification when buying a device  but it s actually not that useful when designing for Android because thinking of screens in terms of pixels ignores the notion of physical size  which for a touch device is really really important   Density independent pixel  dp or dip  allow the designer to create assets that appear in a expected way  no matter the resolution or density of target device   A density independent pixel  dp or dip  is equal to one pixel at the baseline density or 160 dpi  dots per inch    1 px 1dp   160 dpi 160 dpi  2 px 1dp   320 dpi 2x  160 dpi  where   dpi is dots per inch  So  at 320 dpi  1 dp is equal to 2 px   Formula  px dp   dpi 160dpi  Dots per inch  dpi  is a measure of the sharpness  that is  the density of illuminated points  on a display screen  The dots per inch for a given picture resolution will differ based on the overall screen size since the same number of pixels are being spread out over a different space   Working with density independent pixels help us to deal with a situation like where you have two devices with same pixel resolution  but differing amount of space  Suppose in a case  a tablet and phone has the same pixel resolution 1280 by 800 pixels  160 dpi  and 800 by 1280 pixels  320 dpi  respectively   Now because a tablet is at baseline density  160 dpi  its physical and density independent pixels sizes are the same  1280 by 800  The phone on the other hand has a higher pixel density  so it has half as many density independent pixels as physical pixels  So a phone has 400 by 640 density independent pixels  So using a density-independent pixel makes it easier to mentally picture that tablet has much more space than the phone   Similarly  if you have two devices with similar screen size  but different pixel density  say one is 800 by 1280 pixels  320 dpi   and the other is 400 by 640 pixels  160 dpi   we don t need to define totally different layouts for these two devices as we can measure assets in terms of density independent pixel which is same for both devices   800 by 1280 pixels  320dpi  400 by 640 density independent pixel  dp   400 by 640 pixels  160 dpi  400 by 640 density independent pixel  dp   Scale independent pixels sp  is the preferred unit for font size  For accessibility purposes  Android allows users to customize their device s font size  Users that have trouble reading text can increase their device s font size  You can normally find this option in the display setting on your phone or tablet under font size  It s often also available through the accessibility settings   With scale independent pixels  16 sp is exactly the same as 16 dp when the device s font size is normal or 100   But when device s font size is large  for example 125   16 sp will translate to 20 dp or 1 25 times 16   If you use dp as the unit for font size  then that piece of text has a specific physical size no matter if the user has customize device s font size  Using sp units will make a better experience for people with impaired eyesight   Reference  Udacity  Google

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Where to use what  amp  relationship between px  amp  dp  Density-independent pixel  dp  A virtual pixel unit that you should use when defining UI layout  to express layout dimensions or position in a density-independent way  As described above  the density-independent pixel is equivalent to one physical pixel on a 160 dpi screen  which is the baseline density assumed by the system for a  quot medium quot  density screen  At runtime  the system transparently handles any scaling of the dp units  as necessary  based on the actual density of the screen in use  The conversion of dp units to screen pixels is simple  px   dp    dpi   160   For example  on a 240 dpi screen  1 dp equals 1 5 physical pixels  You should always use dp units when defining your application s UI  to ensure proper display of your UI on screens with different densities  Understanding pixel to dp and vice versa is very essential  especially for giving exact dp values to creative team  dp   px   160   dpi  MDPI   160 dpi    Therefore  on MDPI 1 px   1 dp For example  if you want to convert 20 pixel to dp  use the above formula  dp   20   160   160   20  So  20 pixel   20 dp   HDPI   240 dpi - So  on HDPI 1 5 px   1 dp XHDPI   320 dpi - So  on XHDPI 2 px   1 dp XXHDPI   480 dpi - So  on XXHDPI 3 px   1 dp  For example  let us consider Nexus 4  If 24 pixels to be converted to dp and if it is a Nexus 4 screen  developers can convert it to dp easily by the following calculation   dp   24   160   320   12 dp Screen dimension  768 x 1280 pixel resolution  320 ppi or 320dpi  Optional  screen size    4 7 quot  diagonal   Try to get all pixel values in even numbers from the creative team  Otherwise precision lose will happen while multiplying with 0 5   px It is explained above  Try to avoid in layout files  But there are some cases  where px is required  for example  ListView divider line  px is better here for giving a one-pixel line as a divider for all across screen resolutions  sp Use sp for font sizes  Then only the font inside the application will change while device fonts size changes  that is  Display - gt  Fonts on Device   If you want to keep a static sized font inside the app  you can give the font dimension in dp  In such a case  it will never change  Developers may get such a requirement for some specific screens  for that  developers can use dp instead of sp  In all other cases  sp is recommended

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dp is  dip  Use it for everything  margin  padding  etc     Use sp for  text-size  only      To get the same size on different screen densities  Android translates these units into pixels at runtime  so there is no tricky math for you to do     See the difference between px  dp and sp on different screen sizes     Source  Android Programming  The Big Nerd Ranch Guide

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Moreover you should have clear understanding about the following concepts   Screen size      Actual physical size  measured as the screen s diagonal  For simplicity  Android groups all actual screen sizes into   four generalized sizes  small  normal  large  and extra large    Screen density       The quantity of pixels within a physical area of the screen  usually referred to as dpi  dots per inch   For example  a    low  density screen has fewer pixels within a given physical area    compared to a  normal  or  high  density screen  For simplicity    Android groups all actual screen densities into four generalized   densities  low  medium  high  and extra high    Orientation       The orientation of the screen from the user s point of view  This is either landscape or portrait  meaning that the   screen s aspect ratio is either wide or tall  respectively  Be aware   that not only do different devices operate in different orientations   by default  but the orientation can change at runtime when the user   rotates the device    Resolution      The total number of physical pixels on a screen  When adding support for multiple screens  applications do not work directly   with resolution  applications should be concerned only with screen   size and density  as specified by the generalized size and density   groups    Density-independent pixel  dp        A virtual pixel unit that you should use when defining UI layout  to express layout dimensions or   position in a density-independent way  The density-independent pixel   is equivalent to one physical pixel on a 160 dpi screen  which is the   baseline density assumed by the system for a  medium  density screen    At runtime  the system transparently handles any scaling of the dp   units  as necessary  based on the actual density of the screen in use    The conversion of dp units to screen pixels is simple  px   dp    dpi     160   For example  on a 240 dpi screen  1 dp equals 1 5 physical   pixels  You should always use dp units when defining your   application s UI  to ensure proper display of your UI on screens with   different densities    Reference  Android developers site

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Anything related with the size of text and appearance must use sp or pt  Whereas  anything related to the size of the controls  the layouts  etc  must be used with dp   You can use both dp and dip at its places

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Before answering this question let me decrease the number of units first  So here you go  dp or dip are both the same and are known as Density-independent pixels   1  px - stands for pixels  Pixels are a single dot  point on a screen  Generally in the mobile industry it is measured in ppi  pixels per inch   Screen resolution is directly proportional to ppi  the larger the number of pixels per inch the higher the screen resolution   For example  if you draw an image of a size 200 px   200 px  then its appearance must be different on a high-resolution device versus a low-resolution device  The reason is a 200 px image on a low-resolution phone will be look larger than on a high-resolution device   Below images are showing a resolution of the same image on different phones -   Phone with High screen resolution   Phone with Low screen resolution     2  dip or dp - an abstract unit that is based on the physical density of the screen  These units are relative to a 160 dpi screen  so one dp is one pixel on a 160 dpi screen  The ratio of dp-to-pixel will change with the screen density  but not necessarily in direct proportion   Density independence  refers to the uniform display of UI elements on screens with different densities    Image which is showing 80px  left side image  and 80 dp  right-side image   Checkout difference      A dp is equal to one physical pixel on a screen with a density of 160  To calculate dp   dp    width in pixels   160    screen density  3  sp - stands for scalable pixels  Generally sp is used for texts on the UI  and sp preserves the font settings  For example  if a user selected a larger font than 30 sp it will auto scale to appear large according to a user preference

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I will elaborate more on how exactly does dp convert to px    If running on an mdpi device  a 150 x 150 px image will take up 150   150 dp of screen space  If running on an hdpi device  a 150 x 150 px image will take up 100   100 dp of screen space  If running on an xhdpi device  a 150x150 px image will take up 75   75 dp of screen space    The other way around  say  you want to add an image to your application and you need it to fill a 100   100 dp control  You ll need to create different size images for supported screen sizes    100   100 px image for mdpi 150   150 px image for hdpi 200   200 px image for xhdpi

[android] What is the difference between "px", "dip", "dp" and "sp"?

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