Password Entropy Calculator
Measure the randomness and true strength of your passwords using information theory.
Calculate Password Entropy
How to Use This Tool
Understand password entropy and measure true password strength
About Password Entropy
Password entropy measures the randomness and unpredictability of a password using information theory. It's expressed in bits, where each bit doubles the number of possible combinations. Higher entropy means stronger passwords that are harder to crack.
Enter Your Password
Type the password you want to analyze. The tool will process it locally without sending data anywhere.
View Entropy Score
See your password's entropy in bits. Generally, 60+ bits is good, 80+ bits is excellent for most purposes.
Analyze Character Usage
Review how different character types contribute to your password's overall strength and entropy.
Check Crack Times
See estimated time to crack your password using different computing power scenarios.
Entropy Formula
Entropy = log₂(charset_size^password_length). This assumes truly random character selection. Real passwords often have less entropy due to patterns and predictability.
Why Use This Tool?
Scientific Measurement
Uses information theory principles to calculate true password strength.
Detailed Analysis
Breaks down character usage and shows how each type contributes to entropy.
Crack Time Estimates
Shows realistic time estimates for password cracking under different scenarios.
Privacy Protected
All calculations happen locally. Your password never leaves your browser.
Understanding Password Entropy
Length Matters Most
Adding one character to a password dramatically increases entropy. Length is more important than complexity.
Character Set Diversity
Using lowercase, uppercase, numbers, and symbols increases the character set and boosts entropy.
True Randomness
Truly random passwords achieve maximum entropy. Patterns and predictable substitutions reduce it.
Entropy Targets
Aim for 60+ bits for general use, 80+ bits for high-security accounts, 128+ bits for cryptographic keys.
Usability vs Security
Balance high entropy with memorability. Consider using passphrases or password managers.
Human Factor
Remember that calculated entropy assumes perfect randomness. Human-created passwords often have less.