Factorial Calculator
Last updated: November 5, 2026
Calculate n factorial, its digit count, trailing zeros and a simple permutation count.
n factorial
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- Number of digits: —
- Trailing zeros: —
- n permutations taken 2 at a time: —
On this page
Quick summary: Calculate n factorial, its digit count, trailing zeros and a simple permutation count.
Read the complete guide
Updated reference sections in this guide are in English.
What this calculator estimates
Calculate n factorial, its digit count, trailing zeros and a simple permutation count.
How to use it
Enter Whole number n (0–170). Select Calculate to update the results.
How the calculation works
Factorial multiplies every positive whole number from one through n. Trailing zeros are counted from factors of five.
Worked example: starting scenario
| Whole number n (0–170) | 10 |
|---|
| n factorial | 3,628,800 |
|---|---|
| Number of digits | 7 |
| Trailing zeros | 2 |
| n permutations taken 2 at a time | 90 |
Important limitations
The calculator accepts whole numbers from zero through 170 to keep output and browser performance manageable.
Zero factorial and trailing zeros
Factorial multiplies positive integers up to n, with 0! defined as 1. For 10!, the exact value is 3,628,800 and the trailing-zero count is 2. Zeros come from pairs of factors 2 and 5, counted by floor(n/5) + floor(n/25) + … . The displayed ordered-pair count n(n−1) is separate from n!. This form accepts whole numbers from 0 to 170.