math calculator

Factorial Calculator

Compute n! instantly — the product of all positive integers up to n. Essential for permutations, combinations, probability and computer science algorithms.

Important Use Notice

Informational calculator only. Verify important outputs independently before legal, tax, medical, engineering, safety-critical, contractual, employment, or compliance use.

Estimate

Enter job values, review the estimate, then use the decision hints before ordering or quoting.

Enter a non-negative integer

Estimate Results

Enter values to see the result.

Example

5! = 120 (5×4×3×2×1)

Formula

n! = n × (n-1) × (n-2) × ... × 1

Product of all positive integers from 1 to n. 0! defined as 1.

For n > 20 use BigInt to handle large results

Check

Calculating negative factorials (undefined)
Confirm that all inputs use the same unit system expected by the formula.

Next Step

Next Calc

Combinations Calculator

Next: combinations.

Next Calc

Factorial Trailing Zeros Calculator

Next: factorial trailing zeros.

Next Calc

Permutations Calculator

Keep permutations calculator math tidy when a plan, worksheet, or note set needs one quick calculation.

FAQ

Why is 0! defined as 1?

It makes many mathematical formulas consistent (e. g. binomial theorem, permutations).

What is the largest factorial you can calculate?

With BigInt — very large numbers (hundreds or thousands), though display may be limited.