Understanding Password Entropy
Learn what entropy means in password security and see exactly how it's calculated with our interactive tool.
What is Password Entropy?
Entropy is a measure of randomness and unpredictability. In password security, it quantifies how difficult a password would be to crack through brute force attacks.
Higher entropy means more possible combinations an attacker must try, making your password exponentially more secure. Entropy is measured in bits—each additional bit doubles the number of possible combinations.
Charset Size
Password Length
The Entropy Formula
Interactive Entropy Calculator
Try different passwords to see how character types and length affect entropy. Watch the entropy bits increase as you add diversity!
Enter a password above to see entropy calculation
Real-World Examples
Calculation: 268 combinations = 208 billion possibilities = 37.6 bits
Calculation: 9410 combinations (all character types) = 65.5 bits
Calculation: 2728 combinations = 131 bits. Length matters more than complexity!
Why Does Entropy Matter?
Each bit of entropy doubles the work required to crack a password through brute force. Here's what different entropy levels mean:
Can be cracked instantly by modern computers. Never use.
Vulnerable to dedicated attackers with good hardware.
Acceptable for low-security applications but not recommended.
Strong enough to resist brute force attacks. Aim for this minimum.
Key Takeaways
- Length beats complexity: A longer password with simple characters can be stronger than a short complex one.
- Aim for 60+ bits: This provides good security against brute force attacks.
- Character diversity helps: But adding length is more effective than adding special characters.
- Random is better: Predictable patterns reduce effective entropy even if mathematical entropy looks high.