Password Entropy Calculator

Check your passwords and passphrases for entropy with our free password strength calculator. Entropy measures the strength and randomness of your passwords, helping you assess their security against potential attacks.

What is password entropy?

Password entropy is a measure of the randomness and unpredictability of a password to protect it against brute force attacks. Passwords and passphrases with higher entropy are considered more secure. More entropy means it's harder to 'guess' the password because there are more possible combinations. A strong password is created by using a mix of uppercase letters, lowercase letters, numbers, and special symbols, making it more random and unpredictable, compared to a password using common words or just numbers. By having a stronger password coupled with 2FA, you'll be ensuring that your online accounts are safer.

Why is password entropy better than password strength meters?

Password entropy uses mathematics to determine password strength by estimating how difficult it would be to crack. In comparison, password strength meters often enforce specific rules, leading to harder-to-remember passwords and ultimately lower entropy. Password strength meters are only as reliable as the person or company who created them. On the other hand, entropy is independent and remains consistent across all platforms. While password strength meters help educate users about the need for stronger, random passwords, they may not provide much additional protection beyond simply adding a random character at the end of your pre-existing passwords.

Entropy bits

Entropy bits or bits of entropy are used to measure the randomness and unpredictability of a password. One bit of entropy represents a choice between two equally likely options, such as a yes or no answer. When you add another bit of entropy, the number of choices doubles. As you add more bits, the total number of possible combinations increases rapidly, making it increasingly difficult to process all of them and guess the password.

Entropy bits calculation

To calculate password entropy, the password entropy bits equals log2(N^L).

Where N is the unique size of the charater set in the password.

Where L is the length of the password in characters.

And finally, log2 is the logarithm base 2 which converts the number of possible combinations into the bits of entropy number.

Example Password Entropy Strength

The following table illustrates some examples of entropy calculations of passwords of varying strength.