Free AI Password Entropy Calculator
A powerful tool to analyze password strength using mathematical entropy calculations. Understand password security, crack time, and improve your digital safety.
About Password Entropy Calculator
Password entropy is a mathematical measure of password strength and unpredictability. It quantifies how much information is contained in a password and indicates how difficult it would be for an attacker to guess or crack it through brute-force methods.
Measured in bits, entropy increases with both password length and the size of the character set used. A higher entropy value means a more secure password that would take significantly longer to crack using computational attacks. Our Free Password Entropy Calculator helps you understand the real strength of your passwords beyond simple complexity rules.
Understanding password entropy is crucial for cybersecurity because it provides an objective, mathematical basis for evaluating password strength rather than relying on subjective rules or guidelines.
How to Use Password Entropy Calculator Online
Using our online password entropy calculator is quick and secure. Here's how you can analyze your password strength using our free tool:
- Enter your password in the input field (it's processed locally for security).
- Optionally, toggle password visibility using the eye icon.
- For theoretical analysis, check "Use manual character set selection" and choose character types.
- Click the "Calculate Entropy" button.
- Instantly see your password's entropy in bits, strength level, and estimated time to crack.
- Review the detailed breakdown of character set size and security recommendations.
Password Entropy Formula (With Example)
The password entropy calculation is based on information theory and measures the unpredictability of a password. Here's the formula we use:
Password Entropy Formula:
Entropy = L × log₂(R)
Where L = Password Length, R = Character Set Size
The character set size (R) depends on the types of characters used:
- Lowercase letters (a-z): 26 characters
- Uppercase letters (A-Z): 26 characters
- Digits (0-9): 10 characters
- Common symbols (!@#$...): 32 characters
🔎 Example: Let's calculate entropy for the password "P@ssw0rd!":
Password Analysis:
- Length (L): 9 characters
- Contains: Uppercase (P), lowercase (s,s,w,r,d), digits (0), symbols (@,!)
- Character set size (R): 26 + 26 + 10 + 32 = 94 characters
- Entropy = 9 × log₂(94) = 9 × 6.55 = 58.95 bits