`Math.Ceiling`

This C# method rounds up to the next full integer. This means that any number over 1 but under 2 would be rounded to 2.

Math.Ceiling does not return the same result as rounding a number. Math.Ceiling is considered a ceiling function in mathematics.

Input and output

Consider a number like 123.456—we can call Math.Ceiling on it, and the result is rounded up. And the fractional part is removed.

Input:   123.456
Ceiling: 124

Example

The Math.Ceiling method in the System namespace is a static method that returns a value type. The method receives a double or decimal type which is resolved at compile-time.

Detail We see that the number 123.456 has the ceiling of 124. We compute this with Math.Ceiling and display the result.

Info Different versions of Math.Ceiling are called because the compiler applies overload resolution each time.

Result The ceiling of the number 123.456 is 124. The decimal type with value 456.789 has a ceiling of 457.

Detail When you call Math.Ceiling on a negative floating point, the number will be also be rounded up. The ceiling of -100.5 is -100.

using System;

// Get ceiling of double value.
double value1 = 123.456;
double ceiling1 = Math.Ceiling(value1);

// Get ceiling of decimal value.
decimal value2 = 456.789M;
decimal ceiling2 = Math.Ceiling(value2);

// Get ceiling of negative value.
double value3 = -100.5;
double ceiling3 = Math.Ceiling(value3);

// Write values.
Console.WriteLine(value1);
Console.WriteLine(ceiling1);
Console.WriteLine(value2);
Console.WriteLine(ceiling2);
Console.WriteLine(value3);
Console.WriteLine(ceiling3);123.456
124
456.789
457
-100.5
-100

Implementation

We review the implementation of Math.Ceiling. The overload for Math.Ceiling that acts on double types will call into a hidden method that is not represented in managed code.

So Math.Ceiling is likely to be far more optimized than any other method you could develop in C# code.

Detail For decimal, the decimal.Ceiling method is invoked, which calls into the explicit unary negation operator on the decimal type.

Finally The ceiling is found by negating the value, taking its floor, and then negating the result again.

Uses, floor

When we are reporting percentages based on data, using Math.Ceiling or Floor is worthwhile. These methods can help make the output more consistent.

Also When we are trying to display numbers that together represent another number, we can control rounding with Ceiling and Floor.

Math.Ceiling always rounds up a number, even when used on a negative number. We noted the implementation and some possible uses of the ceiling and floor functions.