How to Create a Strong Password

5 min read · Updated September 26, 2026 · by the SolveCalcPro editorial team

Strong passwords are less about clever substitutions and more about length, randomness and not reusing them. This guide explains why, shows how to measure password strength in bits and gives a short list of habits that matter far more than adding an exclamation mark.

Strength is measured in entropy

Entropy counts how many guesses an attacker would need. It equals length × log₂(pool size), where the pool is the number of different characters each position can take. A 12-character password using lowercase letters, uppercase letters and digits (62 characters) has 12 × log₂(62) ≈ 71 bits. Each extra bit doubles the work for an attacker. The password generator shows this figure for every password it makes.

Length beats complexity

Password	Pool	Entropy
8 characters, lowercase only	26	38 bits
8 characters, all types	85	51 bits
12 characters, lowercase only	26	56 bits
16 characters, all types	85	103 bits
20 characters, lowercase only	26	94 bits

Twelve plain lowercase letters are stronger than eight characters of every type, and easier to type. When a site allows it, longer is the cheapest upgrade.

Why humans are bad at randomness

People choose words, names, dates and keyboard walks, then decorate them (Summer2026!). Attack tools model exactly this behaviour, so such passwords fall much faster than their apparent complexity suggests. Real randomness — from a cryptographic random generator — has no pattern to exploit.

Habits that matter most

Unique per account. Reuse turns one breach into many.
Use a password manager so you only memorise one strong master passphrase.
Add two-factor authentication, preferably an authenticator app or security key.
Change a password after a breach or suspicion, rather than on a calendar. Current NIST and NCSC guidance moved away from forced periodic changes.