Decimal.Round() Method in C#

The Decimal.Round() method in C# is used to round a decimal value to the nearest integer or to a specified number of decimal places. This method provides several overloads to handle different rounding scenarios and precision requirements.

Syntax

The Decimal.Round() method has four main overloads −

public static decimal Round(decimal d);
public static decimal Round(decimal d, int decimals);
public static decimal Round(decimal d, MidpointRounding mode);
public static decimal Round(decimal d, int decimals, MidpointRounding mode);

Parameters

• d − The decimal number to be rounded.

• decimals − The number of decimal places in the return value (0 to 28).

• mode − Specification for how to round if the value is midway between two others.

Return Value

Returns a decimal number rounded to the nearest integer or to the specified number of decimal places.

Using Basic Decimal Rounding

Example

using System;

public class Demo {
   public static void Main() {
      decimal val1 = 9.00m;
      decimal val2 = 15.29m;
      decimal val3 = 394949845.14245m;
      
      Console.WriteLine("Original values:");
      Console.WriteLine("Decimal 1 = " + val1);
      Console.WriteLine("Decimal 2 = " + val2);
      Console.WriteLine("Decimal 3 = " + val3);
      
      Console.WriteLine("\nRounded to nearest integer:");
      Console.WriteLine("Value 1 (Rounded) = " + Decimal.Round(val1));
      Console.WriteLine("Value 2 (Rounded) = " + Decimal.Round(val2));
      Console.WriteLine("Value 3 (Rounded) = " + Decimal.Round(val3));
   }
}

The output of the above code is −

Original values:
Decimal 1 = 9.00
Decimal 2 = 15.29
Decimal 3 = 394949845.14245
\nRounded to nearest integer:
Value 1 (Rounded) = 9
Value 2 (Rounded) = 15
Value 3 (Rounded) = 394949845

Using Decimal Rounding with Precision

Example

using System;

public class Demo {
   public static void Main() {
      decimal val1 = 6.59m;
      decimal val2 = 30.127m;
      decimal val3 = 6946649845.25245m;
      
      Console.WriteLine("Original values:");
      Console.WriteLine("Decimal 1 = " + val1);
      Console.WriteLine("Decimal 2 = " + val2);
      Console.WriteLine("Decimal 3 = " + val3);
      
      Console.WriteLine("\nRounded with specified decimal places:");
      Console.WriteLine("Value 1 (1 decimal) = " + Decimal.Round(val1, 1));
      Console.WriteLine("Value 2 (1 decimal) = " + Decimal.Round(val2, 1));
      Console.WriteLine("Value 3 (2 decimals) = " + Decimal.Round(val3, 2));
   }
}

The output of the above code is −

Original values:
Decimal 1 = 6.59
Decimal 2 = 30.127
Decimal 3 = 6946649845.25245

Rounded with specified decimal places:
Value 1 (1 decimal) = 6.6
Value 2 (1 decimal) = 30.1
Value 3 (2 decimals) = 6946649845.25

Using MidpointRounding Options

The MidpointRounding enumeration specifies how to round when a value is exactly halfway between two numbers −

Example

using System;

public class Demo {
   public static void Main() {
      decimal value = 2.5m;
      
      Console.WriteLine("Original value: " + value);
      Console.WriteLine("ToEven (default): " + Decimal.Round(value, MidpointRounding.ToEven));
      Console.WriteLine("AwayFromZero: " + Decimal.Round(value, MidpointRounding.AwayFromZero));
      
      decimal negValue = -2.5m;
      Console.WriteLine("\nOriginal negative value: " + negValue);
      Console.WriteLine("ToEven: " + Decimal.Round(negValue, MidpointRounding.ToEven));
      Console.WriteLine("AwayFromZero: " + Decimal.Round(negValue, MidpointRounding.AwayFromZero));
   }
}

The output of the above code is −

Original value: 2.5
ToEven (default): 2
AwayFromZero: 3

Original negative value: -2.5
ToEven: -2
AwayFromZero: -3

Comparison of Rounding Methods

Conclusion

The Decimal.Round() method provides flexible decimal rounding with options for precision control and midpoint handling. Use MidpointRounding.ToEven for financial calculations to reduce bias, and MidpointRounding.AwayFromZero for standard mathematical rounding.