How to use this calculator
- Enter or choose type.
- The entropy updates as you type. Use Copy result or Share to keep it.
Method
Entropy (bits) = L × log₂ N; Possibilities = N^L
- L
- number of characters or words
- N
- characters in the pool or words in the list
Worked example
- Pool: 26 + 26 + 10 = 62 characters; log₂ 62 = 5.9542 bits each.
- 12 × 5.9542 = 71.45 bits.
- 62¹² = 3.23 × 10²¹ possible passwords.
A random 12-character password from upper and lower case letters and digits has 71.45 bits of entropy.
What the result means
Each extra bit doubles the guesses needed. Compare the result with an attacker’s guess rate in the Password Brute-Force Time Calculator to see what it means in time.
Assumptions and limits
- Every character or word is chosen independently and uniformly at random, as a password manager or dice do.
- Human-chosen passwords have far less entropy than their length suggests, because attackers guess common words and patterns first. This calculator does not rate a password you type.
Questions
Why not type my password in to check it?
Entropy belongs to the method that produced the password, not the string. “Password1!” uses four character types but is among the first guesses any cracker tries.
Words or characters?
Six Diceware words (77.5 bits) beat 12 random alphanumerics (71.5 bits) and are much easier to type and remember.