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A factorial multiplies a whole number by every positive whole number smaller than it — used constantly in probability, combinatorics, and statistics.
This calculator computes the exact factorial of any whole number up to 500, using arbitrary-precision arithmetic so large results stay perfectly accurate.
How it works
Enter a whole number from 0 to 500. The calculator multiplies every whole number from that number down to 1, using arbitrary-precision math so even very large factorials come out exact, not rounded.
- Enter number.
- Click Calculate to see your results.
Examples
A small factorial
5! = 5 × 4 × 3 × 2 × 1 = 120.
A larger factorial
10! = 3,628,800 — factorials grow extremely fast as the number increases.
Who should use it
- Calculating permutations and combinations for a probability or statistics problem.
- Checking a combinatorics homework answer.
Industry applications
- Mathematics and statistics education
- Probability, combinatorics, and computer science
Advantages
- Computes exact results for factorials up to 500!, not rounded approximations.
- Shows the full multiplication chain for smaller numbers.
Limitations
- Only supports non-negative whole numbers, consistent with the mathematical definition of a factorial.
Common mistakes to avoid
- Forgetting that factorials are only defined for non-negative whole numbers.
- Assuming a calculator using standard floating-point math will give an exact answer for large factorials — many lose precision above 20!.
Best practices
- For very large factorials, use a calculator (like this one) built on arbitrary-precision arithmetic rather than a standard calculator, to avoid rounding errors.
Tips
- Factorials grow extremely fast — 20! already has 19 digits, so use arbitrary-precision tools for anything beyond small numbers.