Password Entropy

Calculate the entropy and estimated crack time of a password by character set and length

Password length

Character sets used

Lowercase letters (a–z)Uppercase letters (A–Z)Digits (0–9)Symbols (!@#…)

entropy = length × log₂(pool size)

Entropy

71 bits

Character pool size

Estimated crack time (at 10¹² guesses/sec)

102 years

About this calculator

Calculate the entropy and strength of any password based on its length and character set. Entropy measures unpredictability in bits — more bits mean a harder password to crack by brute force.

Common examples

8 lowercase = 37.6 bits (weak)
12 mixed-case + digits = 71.5 bits (strong)
16 all types = 105 bits (very strong)
4-digit PIN = 13.3 bits (very weak)
20 lowercase = 94.0 bits (strong)