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: September 19, 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.
Where is factorial on a TI-30XS or TI-34 calculator?
On the TI-30XS MultiView and TI-34 MultiView, enter the number first, press prb, choose 3: !, and press enter. For example, 5 prb 3 enter returns 120. TI documents factorial inputs from 0 through 69 on these models.
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 tools and references
Factorials also appear in nPr and nCr. See the combinations and permutations examples for worked formulas, or use the prime factorization calculator with steps to decompose a whole number.