Password Strength Checker
Measure password entropy in bits and get a strength rating. Runs entirely in your browser, nothing is sent anywhere.
Independently verified for accuracy
Calculator by Toolsloft ↗- Character pool
- 94
- Entropy
- 111.43 bits
- Rating
- Strong
Check how strong a password is by measuring its entropy, the number of bits an attacker would have to guess through. It reads which character types you used, works out the pool size, and rates the result. Everything runs in your browser, so the password never leaves your device.
How this is calculated
Entropy is length times the base-2 logarithm of the character pool size, where the pool is 26 for lowercase, 26 for uppercase, 10 for digits, and 32 for symbols. Ratings follow common entropy thresholds: under 28 bits very weak, 28 to 35 weak, 36 to 59 fair, 60 to 127 strong, and 128 or more very strong.
How to use
- Type or paste a password into the box.
- Read the character pool size, the entropy in bits, and the strength rating.
- Add length or more character types to raise the entropy.
Examples
- password:
26 chars, 37.6 bits, Fair - Tr0ub4dor&3xample:
94 chars, 111.43 bits, Strong
FAQ
- Is my password sent anywhere?
- No. The check runs entirely in your browser with JavaScript. Nothing is uploaded, logged, or stored.
- Does high entropy guarantee a safe password?
- Entropy measures resistance to brute force, assuming the password is random. A common word or a known phrase can still be guessed quickly even at a high bit count, because attackers try dictionaries first. Length plus unpredictability is what matters.
- Why does adding one symbol help so much?
- A symbol widens the character pool from 62 to 94, and every character then carries more entropy. Adding length helps even more, since entropy grows directly with the number of characters.