Password Entropy Calculator
Estimate a password's strength in bits of entropy from its length and the character set used, plus a rough crack-time indicator.
Your results
Calculation breakdown
- Character pool size
- sum of selected character set sizes
- Entropy
- length × log2(pool size)
- Average crack time
- (pool size^length ÷ 2) ÷ guesses per second
Worked example
A 12-character password using lowercase, uppercase and digits has a pool of 62 characters, giving entropy of 12 × log2(62) ≈ 71.4 bits.
Assumptions
- Assumes a purely random password; real human-chosen passwords are often far weaker than their theoretical entropy suggests.
- Crack-time is an indicative order-of-magnitude estimate for brute-force guessing only.
- Not a substitute for using a reputable password manager.
How this calculator works
Estimate password entropy (a measure of how hard a password is to guess) from its length and character variety, and see an indicative time to brute-force it at a stated guesses-per-second rate.
Frequently asked questions
What is a good entropy value?
As a rough guide, above 60 bits is considered reasonably strong for most personal accounts, with 80+ bits recommended for higher-value accounts.
Is a long password always stronger than a complex short one?
Generally yes — length contributes more to entropy than adding a few extra character types to a short password.
Is the crack-time estimate realistic?
It's an indicative order-of-magnitude figure only; real attacks may use smarter guessing (dictionaries, patterns) rather than pure brute force.