What this calculator does
Password strength works out entropy in bits and how long a brute force would take. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaEntropy = length × log₂(character set size); average time to crack = 2^(entropy−1) / guesses per second
The inputs explained
| Field | What to enter |
|---|---|
| Password length | A number. Starts at 12. |
| Character set | Choose from Lowercase only (26), Upper and lower (52), Letters and digits (62), All keyboard characters (94). |
| Guesses per second an attacker manages | A number. Starts at 10000000000. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with password length
Every other input is held at the calculator’s starting values while password length varies. Select any row to load that scenario into the calculator.