Password Entropy Calculator

Entropy is the honest way to compare password policies. Instead of arguing about whether symbols matter, you can compute exactly how much a rule adds — and most mandatory complexity rules add surprisingly little.

Set a length and a character set below. The calculator reports bits, the number of possible combinations, and the expected time to exhaust half of that space at 10^11 guesses per second.

How to use it

1. Enter the length a system allows.
2. Tick the character classes it permits.
3. Compare two policies by changing one variable at a time.

Reading the numbers

Bits add up: each extra character multiplies the space by the set size, which is the same as adding log2(set size) bits. That is why a 12-to-16 character increase is worth far more than switching from letters-only to full symbols.

The combination count is included because it is more intuitive than bits for many people. 62^12 looks large until you notice an offline attacker covers it in days; 88^16 looks similar in shape but is 30 orders of magnitude larger.

Reviewed 2026-10-21. This tool runs entirely in your browser — no server, no account, and nothing you generate is stored.