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Digital Forensics · Tools
Calculate password entropy in bits, keyspace size and time to crack at a given attack rate.
H = L × log₂(N)
Character set and attacker capability
Entropy
78.7bits
H = L x log2(N) = 12 x log2(94) = 78.7 bits
This assumes a password chosen uniformly at random from the character set. A human-chosen password of the same length and set has far less real entropy, because dictionary and rule-based attacks reach it long before brute force would.
Entropy measures the search space, not real-world resistance. Reused, leaked, or pattern-based passwords fall instantly regardless of computed entropy, and a slow hash such as bcrypt or Argon2 changes the answer by orders of magnitude. Use this to compare policies, not to certify a specific password as safe.
Entropy measures how large a search space a password occupies: the length multiplied by the base-two logarithm of the character set size. Each additional character multiplies the work, which is why length beats complexity.
Time to crack depends entirely on the attack rate, and that depends on the hash. A fast hash like MD5 falls to billions of guesses per second on a GPU, while bcrypt or Argon2 limits an attacker to thousands.