Draw a Perfect Circle Test
Draw one loop around the dot with your mouse, finger or stylus. You get a roundness score in percent, the average and worst deviation from an ideal circle, and a color heatmap showing exactly where your circle drifted.
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Press and hold, then draw one full loop. Release (or close the loop) to get your score.
How to use the Draw a Perfect Circle Test
- Choose a mode: Around the dot (the classic challenge) or Anywhere, where the center is calculated from your drawing.
- Press and hold on the drawing area with your mouse, finger or pen.
- Draw one full loop without lifting. In dot mode the test ends automatically when you complete 360°.
- Read your score: roundness in %, the average and worst deviation, and the heatmap showing where you drifted.
- Press Draw again to beat your best, or download your circle as a PNG.
How the score works
A perfect circle is the set of points at the same distance r from a center. The test measures how far your stroke strays from that ideal:
- Your stroke is resampled into 360 points spaced evenly along its length, so slow and fast parts count equally.
- The center is the dot (dot mode) or the best-fit center from a least-squares circle fit (anywhere mode).
- The ideal radius r̄ is the mean distance of all points from the center.
- For every point, the deviation is |ri − r̄|. The average of these is the average deviation.
- Roundness = 100% × (1 − average deviation ÷ r̄).
Example: with an ideal radius of 200 px and an average deviation of 8 px, roundness = 100 × (1 − 8 ÷ 200) = 96%. In anywhere mode, a stroke that loops well past a full circle loses 5 points for the overlap.
Score guide
| Roundness | Rating | Average deviation |
|---|---|---|
| 97% and up | Near perfect | Under 3% of the radius |
| 93 – 96.9% | Excellent | 3 – 7% |
| 88 – 92.9% | Very good | 7 – 12% |
| 80 – 87.9% | Good | 12 – 20% |
| 65 – 79.9% | Wobbly | 20 – 35% |
| Below 65% | More of a potato | Over 35% |
Tips for a rounder circle
- Move from the shoulder or elbow, not the wrist. A wrist pivot naturally draws flattened ovals.
- Keep an even speed. Slowing down in one quarter usually creates a bump or a flat side there.
- Look at the center, not your finger. Judging the distance to the dot keeps the radius steady.
- Draw bigger. Small hand wobbles matter less on a large circle, because the score is relative to the radius.
- Check the heatmap. Red in the same place every time (for example the top-left) shows the part of the motion to practise.
Frequently asked questions
How is the roundness score calculated?
Your stroke is resampled into 360 evenly spaced points. For each point the distance to the center is measured, and the average of those distances is the ideal radius. Roundness = 100% − (average absolute deviation from the ideal radius ÷ ideal radius × 100). A circle whose points are on average 3% off the ideal radius scores 97%.
What is the difference between the two modes?
In Around the dot mode the center is fixed at the dot, so your circle must be centered and round, just like the popular online challenge. In Anywhere mode the center is found with a least-squares circle fit, so you are scored only on the shape, wherever and whatever size you draw it.
What is a good score?
Most first attempts land somewhere between 70% and 90%. Above 90% is very good, and 95% or more takes a steady hand and a smooth, even speed. A score of 100% would require every point to sit exactly on the ideal radius, which no freehand circle achieves.
What do the colors on my circle mean?
Each part of the stroke is colored by how far it is from the ideal radius: green is on or very close to it, yellow is about 5% off, and red is 10% or more inside or outside the circle. The dashed line shows the ideal circle for comparison.
Why did it say my circle was not complete?
The test tracks how many degrees your stroke travels around the center. You need at least about 324 degrees (90% of a loop) for a score. If you lift your finger or mouse button early, draw again and go all the way around.
Is it easier with a mouse, trackpad or touch screen?
Most people draw the roundest circles with a finger on a touch screen or with a stylus, because the movement comes from the whole hand. Trackpads are usually the hardest. Drawing from the elbow or shoulder rather than the wrist, at a steady speed, gives smoother results with any device.
Is my drawing uploaded anywhere?
No. The drawing, the scoring and your saved best scores all stay in your browser on this device. Nothing is sent to a server.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.