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
When to use this tool
This tool is designed for quick, practical tasks such as everyday calculations, data formatting, or simple conversions. It is best used when you need fast results without installing software or using complex tools.
When to use
- Quick checks or one-time calculations
- Validating or converting data before using it elsewhere
- Simple tasks that do not require advanced software
When not to use
- Critical financial, legal, or medical decisions
- Large-scale or automated processing
- Situations requiring guaranteed precision beyond basic validation
Always review results before using them in important contexts.
About this tool
This tool helps you evaluate password strength and identify weak patterns. It runs entirely in your browser without sending data to a server.
You can use this tool when creating secure passwords for accounts or checking existing ones. The results should be interpreted as an estimate of strength based on entropy and resistance to guessing attacks.
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.