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)

public static double Round (
	double value,
	int digits
public static double Round (
	double value, 
	int digits
public static function Round (
	value : double, 
	digits : int
) : double
Not applicable.



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


The number of fractional digits in the return value.

Return Value

The number nearest value with a number of fractional digits equal to digits.

Exception typeCondition


digits is less than 0 or greater than 15.

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 digits in d to the right of the digits position is halfway between the digit in the digits position, that digit is rounded up if it is odd, or left unchanged if it is even. If the precision of d is less than digits, d 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.

The following example demonstrates rounding to nearest.

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

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

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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