How Password Entropy Measures Security
Security experts measure the strength of a password using a value called **entropy**. Measured in bits, entropy tells you how many guesses a computer would need to try every single combination. Each added bit doubles the complexity.
The Entropy Sizing Formula
To calculate the total entropy (E) of a password, you raise the size of your character pool (R) to the power of the password length (L), then find the base-2 logarithm of the result:
E = Length * log2(Pool Size)
Character Pool Sizes
Selecting more types of characters enlarges the pool size (R), which increases overall strength without forcing you to write exceptionally long passwords:
Lowercase Only 26
Alphanumeric 62
Full Symbol Set 94
No Similars 80