Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Applies only to independently uniform random strings, not human-chosen passwords. Guess rate is supplied; no breach lookup, hashing benchmark or security guarantee.
Example Calculation
- Alphabet size: 62
- Independent characters: 12
- Trial rate: 1000000000 guesses/s
Twelve independently uniform choices from 62 symbols have about 71.45 bits of entropy.
Frequently asked questions
How do I use this calculator?
Enter alphabet size, independent characters, trial rate. The result updates automatically. Use Reset to restore the example values.
What method does it use?
entropy=length log₂(alphabet); average guesses=(alphabet^length+1)/2.. Applies only to independently uniform random strings, not human-chosen passwords. Guess rate is supplied; no breach lookup, hashing benchmark or security guarantee.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.