Password Entropy Calculator
Estimate password entropy from actual password content or from manual assumptions about length and character pool.
The result is a theoretical estimate. Human-chosen passwords often have lower effective entropy than the math suggests.
| Metric | Value |
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Privacy: all calculations run locally in your browser. Passwords are not stored or transmitted.
How it works
Entropy is estimated as length × log2(pool size). The tool also reports the implied search space and a rough time-to-guess estimate using your chosen guess rate.
Examples
- 16 chars from 94 printable characters → much higher entropy than an 8-character lowercase-only password
- Random generated strings → typically closer to theoretical entropy
- Human-chosen passwords → often lower effective entropy than the formula implies
FAQ
- What is password entropy?
Password entropy is a rough measure of unpredictability, often expressed in bits. Higher entropy generally means more guessing effort for an attacker.
- How does this calculator estimate entropy?
It estimates entropy using length and the assumed character pool size, then reports total combinations and rough guess-time estimates under simplified attack assumptions.
- Is entropy the same as strength?
Not exactly. Entropy is a mathematical estimate. Real password strength also depends on reuse, common patterns, leaks, hashing, and attacker constraints.
- Does this tool store my password?
No. Everything runs locally in your browser. Your password is not stored or transmitted.
- Why does actual entropy differ from theoretical entropy?
Real users often choose predictable structures, words, dates, or substitutions. That reduces effective entropy compared with the theoretical maximum.