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Password Entropy Calculator — Real Bits of Entropy, Explained

Type a password to see its entropy calculated in bits — the actual formula (length × log2 of character-set size), shown so you can see exactly why it produces that number, rather than a black-box "strong/weak" label. For a version with visual bit-strength graphing, see Entropy Pro; for the AI-enhanced version with crack-time and passphrase suggestions, see the AI Password Strength Analyzer.

How to use Entropy Calc

  1. Type your password.
  2. Read the calculated entropy in bits.
  3. See the character-set size and length used in the formula.

Frequently asked questions

What is a good entropy score?
Above 60 bits is generally considered strong against offline attacks; above 80 bits is very strong. Below 40 bits is crackable relatively quickly with modern hardware.
How is entropy actually calculated?
Entropy in bits = length × log2(character set size) — a 12-character password using lowercase, uppercase, digits and symbols (94 possible characters) has about 12 × log2(94) ≈ 78.7 bits.
Does this account for dictionary words?
No — this is the pure mathematical entropy formula based on character set and length. A password like "Password123!" scores well on this formula despite being a common, easily guessed pattern; the AI Password Strength Analyzer checks for that separately.

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