Random Password Strength Meter

What is a Random Password Strength Meter?

A Password Strength Meter evaluates how resistant a password is to guessing and brute-force attacks. It analyzes the password's length, character diversity (uppercase, lowercase, digits, symbols), and checks for common patterns, sequences, and dictionary words. The meter provides an instant rating from Weak to Strong and offers suggestions for improvement.

How to calculate password strength manually (the formula)

Password strength can be quantified by entropy: E = L × log&sub2;(N) where L is password length and N is the size of the character set. A password with only lowercase letters has N=26; adding uppercase gives N=52; adding digits gives N=62; adding symbols gives N=95. Entropy below 30 bits is considered weak, 30-60 bits is moderate, and 60+ bits is strong. For example, a 10-character lowercase password has 10 × log&sub2;(26) ≈ 47 bits (moderate).

Example calculation

Password Password123 (11 characters). Character types: uppercase (1), lowercase (8), digits (3). Character set: 26+26+10 = 62. Entropy: 11 × log&sub2;(62) ≈ 65 bits. However, this password contains the common word "Password" and sequential digits "123", so pattern detection correctly downgrades it to Weak. A truly random password like aB7#kL9$zQ2!xR5 (16 chars, all 4 types) would have 16 × log&sub2;(95) ≈ 105 bits and is rated Strong.

Common mistakes

• Using keyboard patterns — Sequences like "qwerty" or "asdfgh" are easily guessed, even though they appear random to users.
• Substituting look-alike characters — Replacing o with 0 or e with 3 (as in "P@ssw0rd") is well-known to attackers and adds negligible strength.
• Assuming length alone guarantees strength — "aaaaaaaaaaaaaaa" is 15 characters but has only 15 × log&sub2;(26) ≈ 70 bits of entropy with zero diversity.

Frequently asked questions