The Excel FACT function returns the factorial of a number — the product of all positive whole numbers up to and including it. FACT(5) = 5×4×3×2×1 = 120.
Syntax
| Argument | Description | |
|---|---|---|
number | Required | A non-negative number. Non-integers are truncated first; negatives return a #NUM! error. |
How to use it
The factorial multiplies every whole number from 1 up to the argument. It grows extremely fast and is the backbone of counting and probability formulas.
Factorials count the number of ways to arrange a set of items (permutations): 5 books can be lined up in FACT(5) = 120 different orders. FACT underpins COMBIN, MULTINOMIAL, and many statistical functions.
Why is 0! = 1? There is exactly one way to arrange zero items (the empty arrangement), so =FACT(0) returns 1 — not 0. This convention keeps combination and permutation formulas consistent.
Try it: interactive demo
Pick a FACT example to see the formula and its result.
Practice workbook
Frequently asked questions
What is a factorial?
=FACT(5) = 5×4×3×2×1 = 120. It counts how many ways a set of items can be arranged.Why does FACT(0) return 1?
What happens with a negative or decimal number?
=FACT(5.9) behaves like =FACT(5) = 120.How does FACT relate to COMBIN?
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