Rounding a variable to two decimal places C#

Question

I am interested in how to round variables to two decimal places. In the example below, the bonus is usually a number with four decimal places. Is there any way to ensure the pay variable is always rounded to two decimal places?

  pay = 200 + bonus;
  Console.WriteLine(pay);

Google search? http://stackoverflow.com/questions/257005/how-do-you-round-a-number-to-two-decimal-places-in-c — eouw0o83hf, Sep 27 '12 at 12:42
wow HomeWork tag?? just saw it now, http://meta.stackexchange.com/questions/147100/the-homework-tag-is-now-officially-deprecated?cb=1 — Habib, Sep 27 '12 at 12:43

score 100 · Accepted Answer · answered Sep 27 '12 at 12:41

100

Use Math.Round and specify the number of decimal places.

Math.Round(pay,2);

Math.Round Method (Double, Int32)

Rounds a double-precision floating-point value to a specified number of fractional digits.

Or Math.Round Method (Decimal, Int32)

Rounds a decimal value to a specified number of fractional digits.

answered Sep 27 '12 at 12:41

Habib

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And make sure you're using a `float`, `double` or `decimal` type, otherwise this won't ever work. – Aidiakapi Sep 27 '12 at 12:42
I am using a double, but it still doesn't work for me. – Kerry G Sep 27 '12 at 12:45
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call it like `pay = Math.Round(pay, 2);` – Habib Sep 27 '12 at 12:48
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Important: this will round 0.005 to 0.00! See why that is in Jon's answer below, which should be the top answer. – Nullius Sep 12 '18 at 08:00

score 36 · Answer 2 · edited Jun 20 '20 at 09:12

You should use a form of Math.Round. Be aware that Math.Round defaults to banker's rounding (rounding to the nearest even number) unless you specify a MidpointRounding value. If you don't want to use banker's rounding, you should use Math.Round(decimal d, int decimals, MidpointRounding mode), like so:

Math.Round(pay, 2, MidpointRounding.AwayFromZero); // .005 rounds up to 0.01
Math.Round(pay, 2, MidpointRounding.ToEven);       // .005 rounds to nearest even (0.00) 
Math.Round(pay, 2);    // Defaults to MidpointRounding.ToEven

(Why does .NET use banker's rounding?)

score 6 · Answer 3 · answered Sep 27 '12 at 12:43

6

decimal pay  = 1.994444M;

Math.Round(pay , 2);

answered Sep 27 '12 at 12:43

Aghilas Yakoub

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Paul Aldred-Bann · Answer 4 · 2012-09-27T13:16:19.720

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You can round the result and use string.Format to set the precision like this:

decimal pay = 200.5555m;
pay = Math.Round(pay + bonus, 2);
string payAsString = string.Format("{0:0.00}", pay);

edited Sep 27 '12 at 13:16

answered Sep 27 '12 at 12:44

Paul Aldred-Bann

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I doubt you can use `pay` in two different senses in the first line! When you already use `Math.Round`, maybe it's not nexessary to use string formatting as well? If you don't want to round the actual number struct, but only want to shorten the string produced, string formatting is a nice thing. In that case, also consider `"F"` or `"F2"` (and `"N"`, `"N2"`) formatting strings, i.e. for example `string.Format("{0:N}", pay)` or equivalently `pay.ToString("N")`. – Jeppe Stig Nielsen Sep 27 '12 at 13:05
@JeppeStigNielsen You're absolutely right about the first line! Amended. Interesting, I'd never used `{0:N}` before, creature of habit I suppose ;o) – Paul Aldred-Bann Sep 27 '12 at 13:12
To explain further, `"F"` rounds to a number of decimals specified by the `NumberFormat` of the current culture of the current thread. This would often be two decimals. `"F2"` always rounds to two decimals. `"N"` and `"N2"` are similar but they also insert group separators according to the culture. For example `(11223344.5566m).ToString("N")` might produce the formatted number `"11,223,344.56"` in some culture. See [Standard Numeric Format Strings](http://msdn.microsoft.com/en-us/library/dwhawy9k.aspx). – Jeppe Stig Nielsen Sep 27 '12 at 13:30

Furqan Safdar · Answer 5 · 2012-09-27T12:50:42.053

2

Use System.Math.Round to rounds a decimal value to a specified number of fractional digits.

var pay = 200 + bonus;
pay = System.Math.Round(pay, 2);
Console.WriteLine(pay);

MSDN References:

edited Sep 27 '12 at 12:50

answered Sep 27 '12 at 12:45

Furqan Safdar

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score 2 · Answer 6 · answered Sep 27 '12 at 12:45

Make sure you provide a number, typically a double is used. Math.Round can take 1-3 arguments, the first argument is the variable you wish to round, the second is the number of decimal places and the third is the type of rounding.

double pay = 200 + bonus;
double pay = Math.Round(pay);
// Rounds to nearest even number, rounding 0.5 will round "down" to zero because zero is even
double pay = Math.Round(pay, 2, MidpointRounding.ToEven);
// Rounds up to nearest number
double pay = Math.Round(pay, 2, MidpointRounding.AwayFromZero);

score 2 · Answer 7 · answered Sep 27 '12 at 12:48

2

Pay attention on fact that Round rounds.

So (I don't know if it matters in your industry or not), but:

float a = 12.345f;
Math.Round(a,2);

//result:12,35, and NOT 12.34 !

To make it more precise for your case we can do something like this:

int aInt = (int)(a*100);
float aFloat= aInt /100.0f;
//result:12,34

answered Sep 27 '12 at 12:48

Tigran

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Math.Round is not accepting a float number as parameter. – Willy David Jr Dec 26 '16 at 06:59

score 1 · Answer 8 · answered Sep 27 '12 at 12:44

1

Console.WriteLine(decimal.Round(pay,2));

answered Sep 27 '12 at 12:44

Jakub Szułakiewicz

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Rounding a variable to two decimal places C#

8 Answers8

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