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Password Entropy Calculator

Measure password strength in bits of entropy from length and character set.

Inputs

Saved Scenarios

— select 2+ to compare

Entropy (bits)

78.7

Spark says

How it's calculated

Formula

Entropy=Length×log⁡2(Charset Size)Entropy = Length \times \log_2(Charset\ Size)
Charset\ Size
— Number of possible characters per position

What is the Password Entropy Calculator?

Entropy measures password unpredictability in bits — each additional bit doubles the number of guesses an attacker needs to try in a brute-force search.

How to use it

  1. 1 Enter the password length.
  2. 2 Select the character set used (lowercase only, mixed case, etc.).

Worked examples

12 characters, all printable ASCII

About 78.7 bits of entropy.

Try it

Limitations

  • •Assumes a truly random password — predictable patterns (dictionary words, keyboard walks) have far less real entropy than this formula suggests.

Frequently asked questions

How much entropy is 'enough'?

60+ bits is generally considered strong for most accounts; higher-security contexts often recommend 80+ bits. This assumes true randomness — a memorable phrase with obvious patterns is weaker than its raw character count implies.