Password Entropy Calculator
Calculate password entropy bits and estimate crack time at different attack speeds. Fully client-side.
Enter a password above to see its entropy and crack time estimates.
Password entropy measures, in bits, how unpredictable a password is based on its length and character variety - higher entropy means exponentially more possible combinations an attacker would need to try. This tool calculates a password's entropy and estimates roughly how long it would take to crack by brute force.
Frequently asked questions
Higher is better - many security guidelines suggest aiming for at least 60-80 bits of entropy for important accounts, though the practical threshold depends on what you're protecting and against what kind of attacker.
It's based on the total number of possible combinations (determined by entropy) divided by an assumed number of guesses an attacker could attempt per second - actual crack time in the real world also depends heavily on the specific system's security measures beyond just the password itself (like rate limiting).
Length is a major factor, but entropy also depends on unpredictability - a long but predictable password (like "passwordpasswordpassword") has much lower real-world entropy than its length alone would suggest, since attackers can exploit the pattern.