How Password Strength Is Measured
This checker analyzes the length and character composition of a password to calculate its entropy in bits and estimate how long it would take to crack under different attack scenarios. No data is sent to any server โ everything runs in your browser.
Strength Levels by Entropy
| Level | Entropy | Example |
|---|---|---|
| Very Weak | 0โ27 bits | 6-digit PIN, common word |
| Weak | 28โ35 bits | 8 lowercase letters |
| Fair | 36โ59 bits | 10-char mixed case |
| Strong | 60โ79 bits | 12-char mixed + symbols |
| Very Strong | 80+ bits | 16+ char mixed |
Why Length Beats Complexity
Each additional character multiplies the total combinations by the entire pool size. An 8-character password using all 94 printable ASCII characters has 94โธ โ 6 quadrillion combinations. A 16-character lowercase-only password has 26ยนโถ โ 4.4 ร 10ยฒยฒ combinations โ over 7 million times more. The practical lesson: use a passphrase (multiple words strung together) rather than a short symbol-heavy password.
What the Attack Speeds Mean
Online attacks are rate-limited by the server โ typically 10 attempts per second. Offline attacks occur when a password database is stolen and hashed values are cracked locally. A modern GPU rig can test over 1 billion bcrypt hashes per second โ or far more for weaker algorithms like MD5. Aim for at least 60 bits of entropy to resist offline GPU attacks for decades.
Frequently Asked Questions
This tool runs entirely in your browser and sends nothing to a server. That said, it's always a good practice to test your password pattern rather than the actual password you use on important accounts.
Entropy measures unpredictability in bits. Formula: entropy = length ร logโ(pool size). At 128+ bits, brute-force attacks are computationally infeasible with any current or foreseeable hardware.
No โ this tool calculates worst-case brute-force time. A password like "football2023" has high character-count entropy but is trivially cracked by a dictionary attack. Avoid real words and predictable patterns regardless of length.