Round Method (Double)

Math.Round Method (Double)


Rounds a double-precision floating-point value to the nearest integral value.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

public static double Round(
	double a


Type: System.Double

A double-precision floating-point number to be rounded.

Return Value

Type: System.Double

The integer nearest a. If the fractional component of a is halfway between two integers, one of which is even and the other odd, then the even number is returned. Note that this method returns a Double instead of an integral type.


For examples and comprehensive usage information about this and other overloads of the Round method, see the Round reference page.

Notes to Callers:

Because of the loss of precision that can result from representing decimal values as floating-point numbers or performing arithmetic operations on floating-point values, in some cases the Round(Double) method may not appear to round midpoint values to the nearest even integer. In the following example, because the floating-point value .1 has no finite binary representation, the first call to the Round(Double) method with a value of 11.5 returns 11 instead of 12.

using System;

public class Example
   public static void Main()
      double value = 11.1;
      for (int ctr = 0; ctr <= 5; ctr++)    
         value = RoundValueAndAdd(value);


      value = 11.5;

   private static double RoundValueAndAdd(double value)
      Console.WriteLine("{0} --> {1}", value, Math.Round(value));
      return value + .1;
// The example displays the following output:
//       11.1 --> 11
//       11.2 --> 11
//       11.3 --> 11
//       11.4 --> 11
//       11.5 --> 11
//       11.6 --> 12
//       11.5 --> 12

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Return to top
© 2015 Microsoft