Entropy Calculator
Calculate the entropy (in bits) of a password based on character pool size and length. Understand brute-force resistance.
Analyzed locally — your password is never transmitted or stored.
How to use the Entropy Calculator
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Type or paste a password.
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Read the entropy in bits.
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Understand brute-force resistance.
What is password entropy?
Entropy measures unpredictability in bits — each bit doubles the number of guesses an attacker needs. A password with 40 bits requires up to 2^40 (≈1 trillion) guesses. This calculator measures entropy from character pool size and length, plus estimates real-world entropy adjusting for common patterns.
Key features
- Entropy in bits from character pool and length
- Real-world entropy estimate (adjusts for patterns)
- Brute-force time estimate
- Character pool detection
Frequently asked questions
How many bits is good?
40+ bits for low-value, 60+ for important, 80+ for high-security like password managers.
Length or complexity?
Length matters more. 16 lowercase chars ≈ 75 bits; 8 mixed chars ≈ 52 bits.
Is my password stored?
No. All calculations happen locally in your browser.