HUMAN–COMPUTER INTERACTION

Fitts's Law Simulator

Test how target distance and target size affect pointing time. Change the parameters, complete randomized 10-trial runs — each run with a different circle size — and compare your measured movement time with the model prediction.

MT = a + b · log₂(D / W + 1) Shannon formulation
Experiment

Pointing task

Click START once to begin a 10-trial run.
Ready for 10 trials
Predicted movement time 437 ms Fitts's Law model
Last movement time — Run a trial
Average movement time — 0 successful trials
Accuracy — 0 misses
Results

Average time by circle size

Measured Predicted
Complete a few trials to populate the chart.
History

Recent trials

#DWIDMeasured
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What it means

Why Fitts's Law matters

Distance increases effort. Targets that are farther away generally take longer to acquire because the pointer must travel farther.

Size reduces effort. Larger targets are easier and faster to hit because they tolerate more pointing error.

Design implication. Frequently used controls should be large enough and positioned where users can reach them with minimal pointer movement.