Decimal.Floor() Method in C#

The Decimal.Floor() method in C# rounds a specified decimal number down to the nearest integer toward negative infinity. This means it always rounds down, even for negative numbers.

Syntax

Following is the syntax −

public static decimal Floor(decimal val);

Parameters

• val − The decimal value to round down to the nearest integer.

Return Value

Returns a decimal value representing the largest integer less than or equal to the specified decimal number.

Using Decimal.Floor() with Positive Numbers

Example

using System;

public class Demo {
   public static void Main() {
      decimal val1 = 25.25m;
      decimal val2 = 11.85m;
      decimal val3 = 7.99m;
      
      Console.WriteLine("Decimal 1 = " + val1);
      Console.WriteLine("Decimal 2 = " + val2);
      Console.WriteLine("Decimal 3 = " + val3);
      Console.WriteLine("Floor (val1) = " + Decimal.Floor(val1));
      Console.WriteLine("Floor (val2) = " + Decimal.Floor(val2));
      Console.WriteLine("Floor (val3) = " + Decimal.Floor(val3));
   }
}

The output of the above code is −

Decimal 1 = 25.25
Decimal 2 = 11.85
Decimal 3 = 7.99
Floor (val1) = 25
Floor (val2) = 11
Floor (val3) = 7

Using Decimal.Floor() with Negative Numbers

Example

using System;

public class Demo {
   public static void Main() {
      decimal val1 = -25.25m;
      decimal val2 = -11.85m;
      decimal val3 = -0.5m;
      
      Console.WriteLine("Decimal 1 = " + val1);
      Console.WriteLine("Decimal 2 = " + val2);
      Console.WriteLine("Decimal 3 = " + val3);
      Console.WriteLine("Floor (val1) = " + Decimal.Floor(val1));
      Console.WriteLine("Floor (val2) = " + Decimal.Floor(val2));
      Console.WriteLine("Floor (val3) = " + Decimal.Floor(val3));
   }
}

The output of the above code is −

Decimal 1 = -25.25
Decimal 2 = -11.85
Decimal 3 = -0.5
Floor (val1) = -26
Floor (val2) = -12
Floor (val3) = -1

Comparison with Math.Truncate()

Example Demonstrating the Difference

using System;

public class Demo {
   public static void Main() {
      decimal val = -3.7m;
      
      Console.WriteLine("Original value: " + val);
      Console.WriteLine("Floor: " + Decimal.Floor(val));
      Console.WriteLine("Truncate: " + Math.Truncate(val));
   }
}

The output of the above code is −

Original value: -3.7
Floor: -4
Truncate: -3

Conclusion

The Decimal.Floor() method always rounds down toward negative infinity, making it useful for financial calculations where you need consistent downward rounding. For negative numbers, this means rounding to a more negative value, which differs from simple truncation.