MOUSE · TOUCH · PEN
Perfect Circle Test
Draw one circle in a single stroke. We measure how far it strays from a perfect circle and score it from 0 to 100.
Global leaderboard Live
The roundest circles drawn by signed-in players, updated live. Tap one to see the drawing.
How it works
Press anywhere in the drawing area with a mouse, finger or stylus and drag around in one continuous stroke.
Release once you're back where you started. Slightly overlapping the start is fine.
Read your score. The dashed line is the best-fitting circle; green parts of your stroke are on it, red parts drift away.
How the score is calculated
Your stroke is resampled evenly along its length, so speed doesn't matter. We fit the circle that best matches it, then measure how far each point sits from that circle relative to its radius. A deviation of 0% scores 100, and a 20% average deviation scores 0. Leaving a gap between the start and end, or stopping short of a full turn, costs extra points.
Tips for a rounder circle
Draw from your elbow or shoulder rather than your wrist, keep a steady speed, and look slightly ahead of your pen. A larger circle is usually easier to keep round than a small one.
Frequently Asked Questions
How does the global leaderboard work?
Sign in and every circle you draw is checked and re-scored on our server. Your best score counts, and the top 10 are shown with their name and the actual drawing. Signing in is optional: without an account your best score is only kept in this browser.
Can I use a touchscreen or drawing tablet?
Yes. The test works with a mouse, trackpad, finger on a touchscreen, or a stylus on a drawing tablet. Pens that report extra samples between frames are captured in full detail.
Is a score of 100 possible?
In theory, yes, but a freehand circle will almost always have some deviation. Anything above 90 is very good, and above 95 is exceptional.
Does the size of my circle matter?
Not for the score: it measures deviation relative to the radius, so a large and a small circle with the same shape score the same. Very small circles are rejected, and bigger circles are usually easier to keep round.