Password Entropy Calculator

Calculate password entropy and estimate brute-force crack times for different attack scenarios.

Local only

PasswordYour password stays local

Privacy notice:

All calculations happen entirely in your browser
Your password is never sent to any server
No data is stored or logged

Password Strength

Enter password

Entropy

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Length

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Charset Size

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Character Sets Detected

Lowercase (a-z) Uppercase (A-Z) Numbers (0-9) Symbols (!@#$...) Space

Brute-Force Time Estimates

Average case (50% probability)

Online (Throttled)

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~10 guesses/sec

Online (Unthrottled)

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~1,000 guesses/sec

Offline (Slow Hash)

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~10,000 guesses/sec (bcrypt)

Offline (Fast Hash)

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~10B guesses/sec (MD5/SHA)

Recommendations

Enter a password to see personalized recommendations.

Shannon entropy Real crack time estimates Pattern detection Privacy-first

How it works

Password entropy measures the unpredictability of a password. Higher entropy means more possible combinations and longer crack times.

Entropy = length × log₂(charset size)
Patterns detected reduce effective entropy
Crack time = 2^(entropy-1) / guesses per second

Quick examples

Weak password

password

Common password - instant crack

Fair password

MyP@ss123

~52 bits - Hours to days offline

Strong password

C0rr3ct-H0rs3-B4tt3ry-St4pl3!

~160+ bits - Centuries+ to crack

Use passphrases for memorable, high-entropy passwords.

Mini FAQ

What is entropy?

Entropy measures randomness in bits. More bits = more possible combinations = harder to crack.

What's a good entropy?

60+ bits is decent, 80+ bits is strong, 100+ bits is excellent for most purposes.

Why different crack times?

Attack speed varies: rate-limited logins are slow; offline attacks with fast hashes are extremely fast.

What patterns are detected?

Common passwords, keyboard patterns (qwerty), sequences (abc, 123), repeated chars, and dates.