Password Strength Checker
Estimate how strong a password is based on its length and character variety.
Inputs
Tested locally in your browser — never sent anywhere.
Strength
Strong
Entropy (bits)
65.5
Est. Offline Crack Time
165 years
Step by step
Detect character classes present in the password
26 lowercase + 26 uppercase + 10 digits
= pool = 62
All analysis runs locally in your browser. The password is never transmitted.
Entropy = length × log₂(pool size)
11 × log₂(62)
= 65.5 bits
Estimated offline crack time at 10 billion guesses/second
2^65.5 ÷ 10,000,000,000
= 165 years
Assumes an offline brute-force attack. Dictionary words, common patterns, and credential breaches are not modelled.
Strength rating
= Strong
How it works
Strength is estimated from entropy — the length multiplied by the base-2 log of the character pool size. More characters and more variety (upper, lower, digits, symbols) exponentially increase the number of possible passwords and the time to crack them.
Formulas
Entropy
Entropy (bits) = password length × log₂(character pool size)
- H
- Entropy in bits
- L
- Password length
- N
- Size of the character pool inferred from the classes present (a–z: 26, A–Z: 26, 0–9: 10, symbols: 32)
Estimated crack time
Crack time ≈ 2^entropy ÷ guesses per second
- t
- Estimated time to exhaust half the search space (seconds)
- H
- Entropy in bits
- G
- Assumed offline attack speed (10 billion guesses/sec)
This is an educational estimate of theoretical strength and does not account for dictionary words, reuse, or breaches. Use a password manager for real accounts.
Frequently Asked Questions
Is my password sent anywhere?
No. The check runs entirely in your browser; the password never leaves your device.
Why does a long simple password beat a short complex one?
Entropy grows linearly with length but only logarithmically with pool size, so adding characters usually helps more than adding symbol variety. A long passphrase is often stronger and easier to remember.