The 30 laws that fix 80% of interface problems. Hick's, Fitts's, Miller's, and more.
Explore the 34 principlesThe 30 laws that fix 80% of interface problems. Hick's Law tells you how many options to show. Fitts's Law sizes your buttons. Miller's Law structures your navigation. These aren't opinions—they're peer-reviewed formulas used by Stripe, Linear, and Notion. Apply them and watch conversion rates, task completion, and user satisfaction metrics improve.
Stop reinventing the wheel. Hick's Law tells you exactly how many options to show. Fitts's Law sizes your buttons. These 30 principles are the shortcuts top designers use—memorize them and you'll solve interface problems in minutes, not meetings.
Vague specs cost you time. When a PM says "make it more intuitive," these principles translate that into concrete implementation: reduce choices, increase target sizes, add system status feedback. Build to spec the first time instead of iterating through subjective feedback cycles.
"Users don't convert" isn't a diagnosis. These principles pinpoint the exact cause: "Form abandonment at step 3 due to Hick's Law violation—too many payment options." Turn mystery metrics into actionable fixes with principles that have been validated across millions of users.
Inside this part
In practice
Recommended first: Part I