Limiting double to 3 decimal places

Question

This i what I am trying to achieve   If a double has more than 3 decimal places  I want to truncate any decimal places beyond the third   do not round    Eg   12 878999 - gt  12 878   If a double has less than 3 decimals  leave unchanged  Eg     125   - gt  125        89 24 - gt  89 24   I came across this command   double example   12 34567  double output   Math Round example  3     But I do not want to round  According to the command posted above   12 34567 - gt  12 346  I want to truncate the value so that it becomes  12 345

User · Answer

In C lang     double truncKeepDecimalPlaces double value  int numDecimals        int x   pow 10  numDecimals       return  double trunc value   x    x

User · Answer

I can t think of a reason to explicitly lose precision outside of display purposes  In that case  simply use string formatting   double example   12 34567   Console Out WriteLine example ToString    000

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You can use   double example   12 34567  double output      double     int   example   1000 0        1000 0

User · Answer

Multiply by 1000 then use Truncate then divide by 1000

User · Answer

Doubles don t have decimal places - they re not based on decimal digits to start with  You could get  the closest double to the current value when truncated to three decimal digits   but it still wouldn t be exactly the same  You d be better off using decimal   Having said that  if it s only the way that rounding happens that s a problem  you can use Math Truncate value   1000    1000  which may do what you want   You don t want rounding at all  by the sounds of it   It s still potentially  dodgy  though  as the result still won t really just have three decimal places  If you did the same thing with a decimal value  however  it would work   decimal m   12 878999m  m   Math Truncate m   1000m    1000m  Console WriteLine m      12 878   EDIT  As LBushkin pointed out  you should be clear between truncating for display purposes  which can usually be done in a format specifier  and truncating for further calculations  in which case the above should work

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Good answers above- if you re looking for something reusable here is the code  Note that you might want to check the decimal places value  and this may overflow   public static decimal TruncateToDecimalPlace this decimal numberToTruncate  int decimalPlaces        decimal power    decimal  Math Pow 10 0   double decimalPlaces         return Math Truncate  power   numberToTruncate     power

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double example   3 1416789645  double output   Convert ToDouble example ToString  N3

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If your purpose in truncating the digits is for display reasons  then you just just use an appropriate formatting when you convert the double to a string   Methods like String Format   and Console WriteLine    and others  allow you to limit the number of digits of precision a value is formatted with   Attempting to  truncate  floating point numbers is ill advised -  floating point numbers don t have a precise decimal representation in many cases  Applying an approach like scaling the number up  truncating it  and then scaling it down could easily change the value to something quite different from what you d expected for the  truncated  value   If you need precise decimal representations of a number you should be using decimal rather than double or float

[c#] Limiting double to 3 decimal places

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