1. What is Password Entropy?

Password entropy is a measurement of how unpredictable a password is, expressed in bits. The higher the entropy, the more secure the password is against brute-force attacks.

2. How Does the Calculator Work?

The calculator uses the password entropy formula:

Where:

• \( Length \) — Number of characters in the password
• \( Alphabet Size \) — Number of possible characters at each position

Explanation: The formula calculates the number of bits needed to represent all possible combinations of the password given its length and character set.

3. Importance of Password Entropy

Details: Password entropy helps evaluate password strength. Higher entropy means more possible combinations, making the password harder to crack. A minimum of 64 bits is recommended for most purposes, with 80+ bits for high-security applications.

4. Using the Calculator

Tips: Enter the password length (number of characters) and the size of the character set used (e.g., 26 for lowercase letters only, 62 for alphanumeric, 94 for all printable ASCII characters).

5. Frequently Asked Questions (FAQ)

Q1: What's considered good password entropy?
A: Generally, 64 bits is adequate, 80 bits is good, and 128+ bits is excellent for most applications.

Q2: How does character set affect entropy?
A: Using more character types (uppercase, lowercase, numbers, symbols) increases alphabet size, which exponentially increases entropy.

Q3: Is entropy the only factor in password security?
A: No, resistance to dictionary attacks and memorability are also important. A long passphrase might have lower entropy but be more secure against certain attacks.

Q4: What's the entropy of a 12-character password with mixed case and numbers?
A: Alphabet size would be 62 (26 lowercase + 26 uppercase + 10 digits), so entropy = 12 × log₂(62) ≈ 71.45 bits.

Q5: How does this relate to password cracking time?
A: Each additional bit doubles the number of possible combinations, making brute-force attacks exponentially harder.