Rounding Off a double value using Math.Round

Question

I have a double value: 0.314285 which I want to Round off to 5 decimal places. From a mathematical point of view my expectant result is: 0.31429. In my code I use the Math.Round with MidPointRounding.AwayFromZero parameter overload, the resultant output being: 0.31428.

Is there another way to implement to have the output result as: 0.31429??

How did you declare the `0.314285` value? Basically, you should read this [article](https://learn.microsoft.com/en-us/dotnet/api/system.math.round?view=netframework-4.8#rounding-and-precision) Using a decimal will solve your problem — Pavel Anikhouski, Jan 19 '20 at 16:25
[Related](https://stackoverflow.com/questions/977796/why-does-math-round2-5-return-2-instead-of-3) — Sнаđошƒаӽ, Jan 19 '20 at 16:32
@Sнаđошƒаӽ This is related to `MidpointRounding`, `Round` uses `MidpointRounding.IsEven` by default, but OP explicitly sets it to `AwayFromZero` — Pavel Anikhouski, Jan 19 '20 at 16:43

Pavel Anikhouski · Accepted Answer · 2020-01-30T07:47:22.877

5

You should read the rounding and precision article. The real representation of your number in memory can be something like 0.3142849999999999, and therefore you are getting 0.31428 result. Using a decimal type can help to solve this issue

var value = 0.314285m;
var result = Math.Round(value, 5, MidpointRounding.AwayFromZero); //0.31429

edited Jan 30 '20 at 07:47

answered Jan 19 '20 at 16:30

Pavel Anikhouski

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Thank you very, yes i tried with a decimal type and it worked. – jdennoh Jan 20 '20 at 05:20

score 0 · Answer 2 · edited Jan 19 '20 at 18:55

0

public static double RoundUp(double i, int decimalPlaces)
{
    var power = Math.Pow(10, decimalPlaces);
    return Math.Ceiling(i * power) / power;
}


RoundDown(0.314285, 5); //0.31429

edited Jan 19 '20 at 18:55

Kevin

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answered Jan 19 '20 at 17:12

Eugene Ogongo

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score -1 · Answer 3 · answered Jan 19 '20 at 18:58

-1

Math.Round(decimal number to round, int number of decimal places)

I think this should work for what you are trying to do.

answered Jan 19 '20 at 18:58

New_developer

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Rounding Off a double value using Math.Round

3 Answers3