security tools 6 min read• Updated 2026-09-04
Understanding Password Entropy: How Length Beats Complexity
Why a 16-character passphrase is vastly more secure than an 8-character password with random symbols.
Table of Contents
What is Password Entropy?
Entropy is the mathematical measure of unpredictability in a password, measured in bits: E = L × log2(R), where L is password length and R is the character pool size.
Every single character added exponentially multiplies the number of guesses an attacker must test in a brute-force attack.
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