Password Entropy Calculator

Entropy measures how unpredictable a password is, in bits. Each extra bit doubles the number of guesses an attacker needs. This calculator looks at the length and the kinds of characters used, works out the entropy of a randomly chosen password of that shape, and estimates the time to crack it online and against a stolen password database. The password never leaves your browser.

How to use Password Entropy Calculator

1. Type or paste a password. It is analysed on your device and not sent anywhere.
2. Read the entropy in bits and the rating.
3. Compare the two crack-time estimates: an online attack (slowed down by the website) and an offline attack on a leaked, fast-hashed database.

When it comes in handy

• Explaining to a team why length beats complexity.
• Choosing a length for generated passwords or passphrases.
• Setting a sensible minimum for a password policy.

Frequently asked questions

How many bits is enough?

Around 60 bits resists online guessing easily; 80 bits or more is a good target for anything that might be attacked offline. A random 16-character password with letters, digits and symbols is over 100 bits.

Why does my "strong" password score high when it is my dog's name and a year?

The formula assumes each character was picked at random. Words, names, dates and keyboard patterns are guessed first by real cracking tools, so such passwords are much weaker than their score. Use a password manager to generate truly random passwords.