Password Entropy Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserBasic
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the password length and the size of the character pool.
- Press Calculate for the entropy in bits and a strength rating.
How it works
Entropy measures how hard a password is to guess: bits = length × log₂(pool size). A bigger pool (adding digits and symbols) and more length both raise it.
As a rough guide: under 40 bits is weak, 60–80 is strong, and 80+ is very strong.
Worked example
12 characters from a 95-character pool. 12 × log₂(95) ≈ 78.8 bits — strong.
Frequently asked questions
What pool size should I use?
26 for lowercase only, 52 for mixed case, 62 with digits, and about 95 with symbols.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.