Password Entropy Formula: A Beginner’s Guide with Examples

When creating a password, it’s easy to underestimate how guessable it is. The password entropy formula helps us understand exactly how resistant a password is to brute-force attacks.

📐 The Formula

Entropy = log2(R^L) = L * log2(R)

Where:

• L = password length
• R = number of possible characters in the character set

🧮 Examples

• Password: abc123
  Set: lowercase (26) + digits (10) = 36
  Length = 6
  Entropy ≈ 6 * log2(36) ≈ 31 bits → Weak
• Password: Tr0ub4dor&3
  Set: lowercase + uppercase + digits + symbols = ~95
  Length = 11
  Entropy ≈ 72 bits → Strong

📊 Entropy Strength Scale

🚀 Try Our Calculator

Want to see the math in action? Use our Password Entropy Calculator to analyze your own passwords instantly.

🔗 Related Tools

• Password Generator
• Entropy Calculator

Understanding entropy gives you the power to create passwords that resist attacks for decades.