How to make CSS width to fill parent

Question

I am sure this problem has been asked before but I cannot seem to find the answer   I have the following markup    lt div id  foo  gt       lt div id  bar  gt          here be dragons      lt  div gt   lt  div gt    My desire is to make foo to have width of 600px  width  600px   and to make bar have the following behaviors    padding-left  2px  padding-right  2px  margin-left  2px  margin-right  2px  outerWidth  100     In other words instead of setting width of bar to 592px I would like to set the outer width of bar to 100  so that it is computed to 592px  The importance here is that I can change foo s width to 800px and bar will calculate when rendered instead of me having to do the math for all these instances manually   Is this possible in pure CSS   Some more fun with it    What if  bar is a table   What if  bar is a textarea   What if  bar is an input  What if  foo is a table cell  td    Does this change the problem or is the problem identical       So far the table bar  input bar has been discussed  I have not seen a good solution for textarea bar  I Think a textarea with no border margin padding with a div wrap might work with the div styled to work as borders for the textarea

User · Answer

Use the styles   left  0px    or and  right  0px    or and  top  0px    or and  bottom  0px    I think for most cases that will do the job

User · Answer

almost there  just change outerWidth  100   to width  auto   outerWidth is not a CSS property   alternatively  apply the following styles to bar   width  auto  display  block

User · Answer

So after research the following is discovered   For a div bar setting display block  width  auto  causes the equivalent of outerWidth 100    For a table bar you need to wrap it in a div with the rules stated below  So your structure becomes    lt div id  foo  gt    lt div id  barWrap  style  border      gt     lt table id  bar  style  width  100   border  0  padding  0  margin  0   gt    This way the table takes up the parent div 100   and  barWrap is used to add borders margin padding to the  bar table  Note that you will need to set the background of the whole thing in  barWrap and have  bar s background be transparent or the same as  barWrap   For textarea bar and input bar you need to do the same thing as table bar  the down side is that by removing the borders you stop native widget rendering of the input textarea and the  barWrap s borders will look a bit different than everything else  so you will probably have to style all your inputs this way

User · Answer

EDIT   Those three different elements all have different rendering rules   So for   table bar you need to set the width to 100  otherwise it will be only be as wide as it determines it needs to be  However  if the table rows total width is greater than the width of bar it will expand to its needed width  IF i recall you can counteract this by setting display  block  important  though its been awhile since ive had to fix that   im sure someone will correct me if im wrong    textarea bar i beleive is a block level element so it will follow the rules the same as the div  The only caveat here is that textarea take an attributes of cols and rows which are measured in character columns  If this is specified on the element it will override the width specified by the css   input bar is an inline element  so by default you cant assign it width  However the similar to textarea s cols attribute  it has a size attribute on the element that can determine width  That said  you can always specifiy a width by using display  block  in your css for it  Then it will follow the same rendering rules as the div   td foo will be rendered as a table-cell which has some craziness to it  Bottom line here is that for your purposes its going to act just like div foo as far as restricting the width of its contents  The only issue here is going to be potential unwrappable text in the column somewhere which would make it ignore your width setting  Also all cells in the column are going to get the width of the widest cell     Thats the default behavior of block level element - ie  if width is auto  the default  then it will be 100  of the inner width of the containing element  so in essence    foo  width  800px    bar  padding-left  2px  padding-right  2px  margin-left  2px  margin-right  2px     will give you exactly what you want

User · Answer

box-sizing  border-box  width  100   padding  5px   box-sizing  border box  makes it so that padding  margin and border are included in the width calculations  MDN

[css] How to make CSS width to fill parent?

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