Password Entropy Calculator
Calculate password strength and entropy to measure resistance against brute force attacks
Password Character Analysis
Standard Character Types
Pool size: 26 characters
Pool size: 26 characters
Pool size: 10 characters
Symbols like !@#$%^&*()_+-=[]|;':",.<>?/~
Custom Character Pools
Custom character set 1
Custom character set 2
Custom character set 3
Password Entropy Results
Password Strength Guidelines
Password Examples
Weak Password: "password"
Length: 8 characters | Pool: 26 (lowercase only)
Entropy: 8 × log₂(26) ≈ 37.6 bits
Crack time: ~2 minutes (very weak)
Better: "Password123"
Length: 11 characters | Pool: 62 (mixed case + digits)
Entropy: 11 × log₂(62) ≈ 65.5 bits
Crack time: ~584 years (fair)
Strong: "MyP@ssw0rd!2024"
Length: 15 characters | Pool: 94 (all character types)
Entropy: 15 × log₂(94) ≈ 98.3 bits
Crack time: ~2.5 × 10²¹ years (very strong)
Character Pool Sizes
Password Security Tips
Use at least 12-15 characters
Mix uppercase, lowercase, numbers, and symbols
Avoid dictionary words and personal information
Use unique passwords for each account
Consider using a password manager
Enable two-factor authentication
⚠️ Important Note
Privacy: This calculator does not require you to enter your actual password. Only enter the count of each character type.
Limitation: High entropy doesn't guarantee security if your password appears in breach databases or uses common patterns.
Understanding Password Entropy
What is Password Entropy?
Password entropy is a measure of password strength that quantifies how difficult it would be for an attacker to guess your password using a brute force attack. It's expressed in bits, where each additional bit doubles the difficulty.
Why It Matters
- •Measures resistance to brute force attacks
- •Helps compare password strength objectively
- •Guides password policy decisions
- •Predicts time needed to crack passwords
Entropy Formula
E = L × log₂(R)
E = Entropy in bits
L = Password length
R = Character pool size
Key Factors
- •Length: Each additional character exponentially increases security
- •Character variety: Larger pools increase entropy per character
- •Randomness: Predictable patterns reduce effective entropy
Attack Scenarios
Online Attacks
Limited by rate limiting and account lockouts. Even weak passwords may be adequately protected.
Offline Attacks
Attackers with password hashes can attempt billions of guesses per second. High entropy becomes crucial.
Beyond Entropy
Dictionary Attacks
Common passwords and patterns are tried first, regardless of entropy. Avoid predictable sequences.
Additional Security
Use unique passwords, enable 2FA, and consider password managers for comprehensive security.