Microsoft® Excel® 2010 Formulas & Functions Inside Out

FACT()

Syntax. FACT(number)

Definition. This function returns the factorial of a number.

Argument

• number (required) The nonnegative number for which you want the factorial. If number isn’t an integer, the decimal places are truncated.

Background. The factorial function is used to calculate partial products of natural numbers. The factorial of a number n is the result of the product of all positive integers less than or equal to n.

For example, the factorial of the number 4 is calculated as:

4! = 1 • 2 • 3 • 4 = 24

The formula is:

n! = n • (n – 1) • (n – 2) •...• 3 • 2 • 1

Note that the factorial of zero is defined: 0! = 1.

Example. In combinatorics, factorials are important because n! is the number of possibilities to arrange n discriminable elements.