Password Entropy Calculator

The Password Entropy Calculator measures a password’s entropy and estimated crack time, shows the character pool it draws on, and suggests ways to strengthen it. It is for anyone wanting a numeric sense of how strong a password really is.

Entropy in bits is a more objective measure of strength than a vague rating. Calculating it locally gives that number with the password kept entirely private.

1. Type or paste the password to measure.
2. Read its entropy in bits and the character pool it uses.
3. Check the estimated crack time.
4. Apply the suggestions to raise the entropy.
5. Re-measure until it reaches a comfortable level.

• Entropy measurement in bits
• Character-pool breakdown
• Estimated crack time
• Improvement suggestions

• Putting a number on how strong a password is
• Understanding how length raises entropy faster than symbols
• Comparing passphrases against random strings
• Teaching the maths behind password strength

• Increase length first; each added character raises entropy more than swapping symbols.
• Aim well above the minimum, since estimates assume an attacker with fast hardware.
• Pair strong entropy with uniqueness — never reuse even a high-entropy password.

• Assuming entropy alone guarantees safety; a high-entropy password reused everywhere is still risky.
• Padding with predictable sequences, which adds length but little real entropy.
• Reading the crack time as exact when it rests on assumptions about attacker speed.