Fitts’s Law: The Science Behind Fast and Easy Design When you tap on your phone, press an elevator button, or click a “Submit” button on a website, you are experiencing more than just design—you’re engaging with psychology and mathematics. One of the most important principles that explains why some interactions feel smooth while others feel clumsy is Fitts’s Law . 📖 A Little History Fitts’s Law was introduced in 1954 by psychologist Paul Fitts , who studied how people move when selecting physical targets. His experiments showed a clear pattern: the time to hit a target increases with distance and decreases with size . This insight became a foundation for human-computer interaction (HCI) , ergonomics , and UI/UX design . Today, Fitts’s Law guides how everything from smartphone apps to airplane cockpits are designed. 🔢 What is Fitts’s Law? At its core, Fitts’s Law predicts the time required to move to and select a target . The formula is: T = a + b ⋅ log 2 ( 1 + D W ) ...