What is Password Entropy and Why It Matters for Your Security

Not all passwords are created equal. Entropy tells you why.

You've probably seen password strength meters that say "weak", "medium", or "strong". But what do they actually mean?

Password entropy is the scientific measure of how unpredictable your password is. It's measured in bits. More bits = harder to crack.

How Entropy Is Calculated

Entropy = password length × log₂(character pool size)

The character pool depends on what types of characters you use:

Lowercase only (a-z): pool of 26
+ Uppercase (A-Z): pool of 52
+ Numbers (0-9): pool of 62
+ Symbols (!@#$): pool of 95

Entropy Benchmarks

< 30 bits — Very weak. Crackable in seconds
30-40 bits — Weak. Crackable in minutes to hours
40-55 bits — Fair. Crackable in days
55-70 bits — Strong. Years to crack
70+ bits — Very strong. Decades to centuries

Examples

password123 → ~38 bits (weak)
MyP@ssw0rd! → ~45 bits (fair)
Correct-Horse-Battery-Staple → ~78 bits (very strong)
Xk9#mP2$vL8@nQ5!rT1 → ~108 bits (very strong)

Check Your Password

Use our free Password Entropy Calculator in your dashboard. It runs entirely in your browser — nothing is sent to our server.