Password Entropy Calculator
Password Entropy FAQ
What is password entropy?
Password entropy measures the unpredictability of a password in bits. The higher the entropy, the stronger the password.
How is entropy calculated?
Entropy is based on the size of the character set and the password length. Formula: Entropy = length × log2(characterSetSize).
What is a good entropy value?
40–60 bits is considered moderate, 60–80 bits strong, and 80+ bits very strong.
Understanding Password Entropy
Password entropy is a mathematical measure of password strength. It considers both the length of the password and the variety of characters used. A longer password with mixed character sets has higher entropy, making it harder for attackers to guess or brute force.
For example, an 8-character password using only lowercase letters has far less entropy than a 16-character password using lowercase, uppercase, numbers, and symbols. The difference can mean the password takes seconds to crack versus billions of years.
Use this tool to instantly calculate the entropy of your password and improve your online security by adopting stronger, more resilient passwords in 2025.