Math.Round Method (Double, Int32) (System)

.NET Framework Class Library

Math..::.Round Method (Double, Int32)

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

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

Syntax

Visual Basic (Declaration)

Public Shared Function Round ( _
    value As Double, _
    digits As Integer _
) As Double

Visual Basic (Usage)

Dim value As Double
Dim digits As Integer
Dim returnValue As Double

returnValue = Math.Round(value, digits)

public static double Round(
    double value,
    int digits
)

Visual C++

public:
static double Round(
    double value, 
    int digits
)

JScript

public static function Round(
    value : double, 
    digits : int
) : double

Parameters

value: Type: System..::.Double
A double-precision floating-point number to be rounded.

digits: Type: System..::.Int32
The number of fractional digits in the return value.

Return Value

Type: System..::.Double
The number nearest to value that contains a number of fractional digits equal to digits.

Exceptions

Exception	Condition
ArgumentOutOfRangeException	digits is less than 0 or greater than 15.

Remarks

The digits parameter specifies the number of fractional digits in the return value and ranges from 0 to 15. If digits is zero, an integer is returned.

The maximum total number of integral and fractional digits that can be returned is 15. If the rounded value contains more than 15 digits, the 15 most significant digits are returned. If the rounded value contains 15 or fewer digits, the integral digits and as many fractional digits as the digits parameter specifies are returned.

If the value of the first digit in value to the right of the digits decimal position is 5, the digit in the digits position is rounded up if it is odd, or left unchanged if it is even. If the precision of value is less than digits, value is returned unchanged.

The behavior of this method follows IEEE Standard 754, section 4. This kind of rounding is sometimes called rounding to nearest, or banker's rounding. It minimizes rounding errors that result from consistently rounding a midpoint value in a single direction. To control the type of rounding used by the Round(Double, Int32) method, call the Math..::.Round(Double, Int32, MidpointRounding) overload.

Examples

The following example demonstrates rounding to nearest.

Visual Basic

Math.Round(3.44, 1) 'Returns 3.4.
Math.Round(3.45, 1) 'Returns 3.4.
Math.Round(3.46, 1) 'Returns 3.5.

Math.Round(4.34, 1) ' Returns 4.3
Math.Round(4.35, 1) ' Returns 4.4
Math.Round(4.36, 1) ' Returns 4.4

Math.Round(3.44, 1); //Returns 3.4.
Math.Round(3.45, 1); //Returns 3.4.
Math.Round(3.46, 1); //Returns 3.5.

Math.Round(4.34, 1); // Returns 4.3
Math.Round(4.35, 1); // Returns 4.4
Math.Round(4.36, 1); // Returns 4.4

Visual C++

Math::Round(3.44, 1); //Returns 3.4.
Math::Round(3.45, 1); //Returns 3.4.
Math::Round(3.46, 1); //Returns 3.5.

Math::Round(4.34, 1); // Returns 4.3
Math::Round(4.35, 1); // Returns 4.4
Math::Round(4.36, 1); // Returns 4.4

JScript

System.Math.Round(3.44, 1) //Returns 3.4.
System.Math.Round(3.45, 1) //Returns 3.4.
System.Math.Round(3.46, 1) //Returns 3.5.

System.Math.Round(4.34, 1) // Returns 4.3
System.Math.Round(4.35, 1) // Returns 4.4
System.Math.Round(4.36, 1) // Returns 4.4

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Reference