Math.Floor() Method in C#

The Math.Floor() method in C# returns the largest integral value that is less than or equal to the specified number. It rounds down to the nearest integer, which is particularly important to understand when working with negative numbers.

Syntax

The Math.Floor() method has two overloads −

public static decimal Floor(decimal val);
public static double Floor(double val);

Parameters

• val − A decimal or double number to be rounded down to the nearest integer.

Return Value

Returns the largest integer less than or equal to val. The return type matches the input type (decimal or double).

Using Math.Floor() with Decimal Numbers

Example

using System;

public class Demo {
   public static void Main() {
      decimal val1 = 7.10M;
      decimal val2 = -79.89M;
      decimal val3 = 15.99M;
      
      Console.WriteLine("Math.Floor(7.10) = " + Math.Floor(val1));
      Console.WriteLine("Math.Floor(-79.89) = " + Math.Floor(val2));
      Console.WriteLine("Math.Floor(15.99) = " + Math.Floor(val3));
   }
}

The output of the above code is −

Math.Floor(7.10) = 7
Math.Floor(-79.89) = -80
Math.Floor(15.99) = 15

Using Math.Floor() with Double Numbers

Example

using System;

public class Demo {
   public static void Main() {
      double val1 = 8.9;
      double val2 = 88.10;
      double val3 = -31.98;
      double val4 = 0.5;
      
      Console.WriteLine("Math.Floor(8.9) = " + Math.Floor(val1));
      Console.WriteLine("Math.Floor(88.10) = " + Math.Floor(val2));
      Console.WriteLine("Math.Floor(-31.98) = " + Math.Floor(val3));
      Console.WriteLine("Math.Floor(0.5) = " + Math.Floor(val4));
   }
}

The output of the above code is −

Math.Floor(8.9) = 8
Math.Floor(88.10) = 88
Math.Floor(-31.98) = -32
Math.Floor(0.5) = 0

Comparison with Related Methods

Conclusion

The Math.Floor() method always rounds down to the nearest integer, returning the largest integral value less than or equal to the input. Remember that for negative numbers, this means moving further away from zero (e.g., -4.3 becomes -5).