Password Entropy Calculator
Enter a password to see a transparent theoretical character-set estimate and local pattern notes. The input stays in this browser and is never checked against breach data or converted into a real-world crack-time claim.
A QUICK WALKTHROUGH
How to use this tool
- Enter a password locally.
- Review the detected character set and theoretical bits per character.
- Read the local pattern notes, then clear the field when finished.
Transparent estimate
Theoretical entropy is length × log2(detected character-set size). It assumes independent, uniformly selected characters; real passwords often do not meet that assumption.
Local pattern notes
The calculator flags repeated characters, sequences, and common password fragments as visible limitations. These are local heuristics, not a breach lookup or crack-time prediction.
Private and bounded
The password is processed only in this browser, is not logged or persisted, and is limited to 256 characters. Clear the field when you finish, especially on a shared device.
GOOD TO KNOW
Common questions
Does this check leaked passwords?
No. It never contacts a breach database or remote service.
Does it tell me how long cracking will take?
No. It reports theoretical bits and local pattern notes only; real attack conditions vary too much for a time claim.
What does the entropy number assume?
It assumes every character was independently and uniformly selected from the detected character set, which may not describe a human-made password.