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

0
Characters
0
Pool Size
0.0
Bits Entropy
None
Strength

Password Strength Guidelines

Very Weak (0-25 bits): Easily cracked in seconds/minutes
Weak (25-50 bits): Could be cracked in hours/days
Fair (50-60 bits): Somewhat secure for basic accounts
Good (60-80 bits): Reasonably secure for most accounts
Strong (80+ bits): Very secure for sensitive accounts

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

Lowercase (a-z)26
Uppercase (A-Z)26
Digits (0-9)10
Mixed case52
Alphanumeric62
All printable ASCII94

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.