Password Strength Checker

What this calculator does

Every input on this password strength checker maps to a real decision, so the output is something you can act on immediately, not a rough ballpark you'll have to double-check elsewhere.

Estimates password strength in bits of entropy.

Runs entirely in your browser — no data leaves your device.

Includes a copy-ready summary and printable PDF view.

Category: Developer & Utility

Inputs required: 1

How to use the Password Strength Checker

Enter your input.
The result updates automatically.
Copy or share the result.

The formula

Entropy ≈ length × log2(pool size).

Worked example

'password' has ~37 bits; a 16-char random has ~100.

Common mistakes

Confusing complexity with length
Using dictionary words
Reusing passwords

When to use it

Use before setting an important password.

Pro tips for the Password Strength Checker

Round-trip check: reverse the inputs to confirm the formula matches what you'd compute by hand.
Bookmark this page: the URL and inputs are all you need to reproduce the exact result later.
Save your favorite scenarios by clicking the star icon — they're stored locally, no account needed.

Frequently asked questions

›Bits needed?

80+ bits is currently strong.

›Passphrase?

4 random words ≈ 44 bits per Diceware.

›Breach check?

haveibeenpwned.com.

›Best practice?

Password manager + 2FA.

›Change often?

Only when breached.

›How accurate is this password strength checker?

The formulas match the standard textbook definition shown above. Rounding is applied only for display; underlying computation uses full floating-point precision. For regulated developer & utility decisions, always confirm with a qualified professional.

›Can I embed the Password Strength Checker on my site?

Embedding isn't public yet, but you can link directly to this page — the URL is stable and shareable.

Embed this calculator

Drop the Password Strength Checker into your own site or blog post. Free to use — a small “Powered by CalcPilot” link is appreciated.

<iframe src="https://calcpilot.tools/calculators/password-strength-checker?embed=1" width="100%" height="720" style="border:1px solid #e5e7eb;border-radius:12px;max-width:720px;" loading="lazy" title="Password Strength Checker — CalcPilot"></iframe>