How to Do a Factorial on a Calculator
Enter the whole number, choose the x! or n! function, and evaluate. If your calculator has no factorial key, multiply down to 1 manually—or use the exact calculator below.
Written and checked by TheToolNet Editorial Team · Last reviewed: August 22, 2026 · How we check math tools
For example, 5! = 5 × 4 × 3 × 2 × 1 = 120. By definition, 0! = 1.
Exact factorial calculator
Calculate any non-negative integer from 0 through 1,000. The exact integer is not rounded.
How to calculate factorial on a scientific calculator
- Enter a non-negative whole number, such as 6.
- Find x! or n!. It may be a secondary label reached with Shift or 2nd, or inside a probability menu.
- Press the factorial function, then press equals if your model requires it.
- For 6!, the display should show 720.
Menu names vary, so use the key legend or manual for your exact model. A factorial usually works only for non-negative integers and may overflow once the result exceeds the calculator’s display range.
How to do factorials on a basic calculator
Without an x! key, type the descending product. For 7!, enter 7 × 6 × 5 × 4 × 3 × 2 × 1. You can omit the final multiplication by 1. For larger values, work in stages and write down intermediate results to avoid a mistyped factor.
Factorial calculation examples
| Expression | Expansion | Result |
|---|---|---|
| 0! | Empty product | 1 |
| 1! | 1 | 1 |
| 5! | 5 × 4 × 3 × 2 × 1 | 120 |
| 10! | 10 × 9 × … × 2 × 1 | 3,628,800 |
The recurrence n! = n × (n − 1)! provides a quick check. For example, 10! ÷ 10 must equal 9!.
Common errors and calculator limits
- Using a decimal or negative integer: the elementary factorial n! is defined here only for non-negative integers.
- Confusing ! with logical NOT: programming languages may use the same symbol differently.
- Reading scientific notation as exact: many calculators round large factorials. The browser tool above keeps the full integer through 1,000!.
- Forgetting 0!: zero factorial equals one, not zero.
Frequently asked questions
What does ! mean after a number?
It means factorial: multiply that whole number by every smaller positive integer.
Why is 0! equal to 1?
It is the value of an empty product and makes the recurrence n! = n(n − 1)! work at n = 1.
Can a basic calculator do factorials?
Yes. Enter the descending multiplication manually if there is no dedicated factorial function.
Why does my calculator show an error for a large factorial?
The exact result may exceed its numeric or display range. Use scientific notation or an arbitrary-precision tool such as the calculator above.
Related tool and reference
Factorials are products of whole numbers. For decomposing a number into primes, use the prime factorization calculator with steps.