Password Strength & Entropy Calculator
Check a password's entropy in bits and estimated crack time across realistic attack scenarios. Runs entirely in your browser — nothing is sent anywhere. Free.
Why length beats complexity
Every character you add multiplies the number of guesses an attacker needs; swapping an a for an @ barely moves the needle. "P@ssw0rd!" looks complex and is trivially cracked because it's a known pattern; a five-word passphrase like correct-battery-staple-jungle-radio is far stronger and easier to type. Entropy — measured in bits here — captures this: each extra bit doubles the effort to brute-force.
The catch with any strength meter
This calculates entropy assuming a random password. Real passwords built from dictionary words, names, dates, or keyboard walks are much weaker than their length suggests, because attackers try those patterns and known breach lists first — not brute force from "aaaa". The reliable answer is a password manager generating long random strings for every account, protected by one strong passphrase. See password managers for small-business teams.