FACT function

The FACT function in Excel is used to return the factorial of a number. The factorial of a number n (denoted n!) is the product of all positive integers less than or equal to n. For example, 5! equals 5 × 4 × 3 × 2 × 1 = 120.

Syntax

=FACT(number)

Parameters

• number: A positive integer for which you want to find the factorial. If you enter a non-integer or negative number, the function will return an error.

Return Value

The function returns the factorial of the given number.

Example 1: Factorial of 5

To calculate 5! (factorial of 5):

=FACT(5)

Result: 120
Explanation: 5! = 5 × 4 × 3 × 2 × 1 = 120.

Example 2: Factorial of 0

To calculate 0!:

=FACT(0)

Result: 1
Explanation: By definition, 0! is equal to 1.

Example 3: Factorial of 7

To calculate 7!:

=FACT(7)

Result: 5040
Explanation: 7! = 7 × 6 × 5 × 4 × 3 × 2 × 1 = 5040.

Important Notes

• The FACT function is only defined for non-negative integers (0, 1, 2, 3, …). If you enter a non-integer or negative number, Excel will return a #NUM! error.
• Factorials grow very quickly, so they are often used in mathematical and statistical calculations, particularly in combinatorics (e.g., calculating permutations and combinations).
• For large numbers, Excel might not be able to compute the factorial due to limitations in number size (Excel can handle up to 170! but larger factorials result in an overflow error).