Math.Round Method (Double)


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

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

Public Shared Function Round (
	a As Double
) As Double


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.

Module Example
   Public Sub Main()
      Dim value As Double = 11.1
      For ctr As Integer = 0 To 5    
         value = RoundValueAndAdd(value)

      value = 11.5
   End Sub

   Private Function RoundValueAndAdd(value As Double) As Double
      Console.WriteLine("{0} --> {1}", value, Math.Round(value))
      Return value + .1
   End Function   
End Module
' 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 8
.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
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