Factorial Calculator

Free factorial calculator supporting n! up to 1000!, double factorial n!!, subfactorial !n, and trailing zeros — 100% client-side. 100% serverless.

🔒 100% Private

⚡ Completely Free

🌐 Runs in Browser

📦 Export Ready

Enter n — A number from 0 to 1000.
Calculate — See n!, n!!, !n, digit count, and trailing zeros.
Copy — Copy results to clipboard.

Calculate factorials up to 1000! using BigInt for exact precision. Also computes double factorial (n!!), subfactorial (!n for derangements), digit count, and trailing zeros.

Features

Exact BigInt computation up to 1000!
Double factorial n!!
Subfactorial !n (derangements)
Trailing zeros and digit count

Privacy

All calculations run in your browser.

Frequently Asked Questions

What is the maximum number?

1000. The calculator uses BigInt for exact precision with arbitrarily large numbers.

What is a double factorial?

n!! = n × (n-2) × (n-4) × ... down to 1 or 2.

What is a subfactorial?

!n counts derangements — permutations where no element appears in its original position.

Is my data safe?

Yes. 100% in your browser.

Factorial Calculator — Free n! Calculator with BigInt