How do you round a number to two decimal places in C#?

c# decimal rounding bankers-rounding

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Solution 1

Here's some examples:

decimal a = 1.994444M;

Math.Round(a, 2); //returns 1.99

decimal b = 1.995555M;

Math.Round(b, 2); //returns 2.00

You might also want to look at bankers rounding / round-to-even with the following overload:

Math.Round(a, 2, MidpointRounding.ToEven);

There's more information on it here.

Solution 2

Try this:

twoDec = Math.Round(val, 2)

Solution 3

If you'd like a string

> (1.7289).ToString("#.##")
"1.73"

Or a decimal

> Math.Round((Decimal)x, 2)
1.73m

But remember! Rounding is not distributive, ie. round(x*y) != round(x) * round(y). So don't do any rounding until the very end of a calculation, else you'll lose accuracy.

Solution 4

Personally I never round anything. Keep it as resolute as possible, since rounding is a bit of a red herring in CS anyway. But you do want to format data for your users, and to that end, I find that string.Format("{0:0.00}", number) is a good approach.

Solution 5

Wikipedia has a nice page on rounding in general.

All .NET (managed) languages can use any of the common language run time's (the CLR) rounding mechanisms. For example, the Math.Round() (as mentioned above) method allows the developer to specify the type of rounding (Round-to-even or Away-from-zero). The Convert.ToInt32() method and its variations use round-to-even. The Ceiling() and Floor() methods are related.

You can round with custom numeric formatting as well.

Note that Decimal.Round() uses a different method than Math.Round();

Here is a useful post on the banker's rounding algorithm. See one of Raymond's humorous posts here about rounding...

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