Password Entropy Calculator
Calculate password entropy in bits to measure password strength against brute-force attacks. Code never leaves your device — formatting and validation run locally in your browser.
How to Use the Password Entropy Calculator
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Frequently Asked Questions
What is password entropy?
Entropy measures password randomness in bits. Higher entropy = harder to crack. It accounts for password length and character set size. 40 bits is weak, 60 bits is moderate, 80+ bits is strong.
How is entropy calculated?
Entropy = log2(character_pool_size ^ password_length). For example, an 8-character password using lowercase + uppercase + digits + symbols (94 chars) has log2(94^8) = 52.6 bits of entropy.
What does the crack time estimate mean?
This tool shows entropy bits, strength, and score only — it does not estimate crack times. For time-to-crack math at attacker guess rates, use the Brute Force Time Estimator.
Should I aim for maximum entropy?
Balance entropy with memorability. A 16-character passphrase with moderate entropy (Diceware-style) is often more practical than a short high-entropy random string. Use a password manager for truly random passwords.
Is my password data stored or transmitted?
No. All calculations run locally in your browser. No password or entropy data is sent to any server.
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Last updated October 2026