Password Entropy Calculator

How to estimate password entropy

1. Type or paste a password into the field. The estimate updates locally as you type.
2. Review the entropy bits. Higher bit counts mean a larger theoretical search space for brute-force guessing.
3. Compare crack-time models. Online attacks, fast offline hashes and slow password hashes have very different risk levels.
4. Read the warnings. Repeated characters, common words and short passwords reduce practical security even when the math looks acceptable.

What this calculator measures

The tool estimates entropy from password length and detected character pools: lowercase, uppercase, numbers and symbols. It also flags patterns that make human-generated passwords weaker than random strings with the same length.

When to use it

Use it when comparing passphrases, explaining password policy trade-offs, auditing old credentials or deciding whether a generated password is long enough for a sensitive account.

Important limitations

Entropy estimates are not breach checks. A password can score well and still be unsafe if it has appeared in a leak, was reused, or follows a personal pattern an attacker can guess.