Password Strength Calculator
Estimate password entropy, character space, and time to crack by brute force.
The Password Strength Calculator evaluates the theoretical strength of a password based on its length and character types used. It calculates entropy in bits and estimates brute-force cracking time.
Enter the password length and toggle which character types are included: lowercase (always on), uppercase, numbers, and symbols. The calculator determines the character set size, entropy bits, and estimated cracking time assuming 1 billion guesses per second.
Higher entropy means stronger passwords. Aim for at least 60 bits for important accounts and 80+ bits for critical security. Length is the single most important factor in password strength.
Frequently Asked Questions
What is password entropy?
Entropy measures the unpredictability of a password in bits. Each bit doubles the number of possible combinations. A 40-bit password has 2^40 (about 1 trillion) possible combinations.
What is a strong password?
Tier 4 (80+ bits): Very strong. Tier 3 (60-79 bits): Strong. Tier 2 (40-59 bits): Moderate. Tier 1 (under 40 bits): Weak. Use at least 12 characters with mixed types.
How long would my password take to crack?
The estimate assumes brute force at 1 billion guesses per second. Real attacks may be faster (GPU clusters) or slower (rate limiting). Dictionary attacks can crack common passwords instantly regardless of length.