Can you draw a perfect circle?
Nobody can draw a perfect circle by hand, but you can measure how close you get. When you draw a perfect circle here, your stroke is compared with the circle that fits it best, and the score is 100 minus four times the average distance between them as a percentage of the radius — so a line that strays by 1% of the radius on average scores 96. There is no published table of how round most people’s circles are, so the score is a measurement of your circle, not a ranking against anyone.
You draw one circle in a single stroke, any size from about a coin up and anywhere on the ice, with a finger or a mouse. The stroke ends when you lift, or as soon as it has gone a full turn; a stroke under 330° or too small doesn’t use up a try. You get three tries and the best counts. Each stroke is resampled every 2 pixels so slow stretches don’t count double, then fitted with Kåsa’s least-squares circle refined by Landau’s geometric iterations. Besides the score you get the shake (what is left after the slow bulges are smoothed over about 20°), how oval it came out and in which direction, the gap where the ends meet, and whether you went clockwise.
The tiers — 96 and up, 90, 80 — are our own rough guide, not a norm. It is not a medical test: neurologists do rate tremor from drawings, but those are clinical spiral tasks, and a circle on a phone can’t tell you anything about your health. Screens, cases and dry or damp fingers all change how smoothly a finger slides.
What the test measures
One thing: how far a single hand-drawn stroke strays from a true circle.
The task
- One circle, one stroke, any size (radius at least 60 px) and anywhere on the ice
- Three tries, best one counts; a stroke short of 330° or too small doesn’t use a try
- Measured in screen pixels against the best-fit circle (Kåsa fit, then Landau iterations); only one full turn is judged
Your result
- Your roundness score out of 100, and the average of all three tries
- The perfect circle swept in orange over your groove, blue where you cut inside it and orange where you went out
- Your best circle measured: average distance off the circle, shake, how oval and which way, the gap, and the direction you drew
- All three circles side by side, with the gaps drawn three times bigger
- A shareable card and a link that asks a friend to draw a rounder one
Before you start
- About a minute; free, no sign-up
- A finger on a phone or tablet, or a mouse; there is no keyboard way to draw
- Your stroke is scored in your browser; a challenge link carries your score after the # in the address
Perfect circle FAQ
Is this test free? Do I need to sign up to see my result?
Yes, it’s free, and there’s nothing to sign up for: no account, no email, no payment. Your result appears on this page the moment you finish, and you can share it or play again straight away.
How is the perfect circle score calculated?
The perfect circle score is 100 minus 4 × the root-mean-square distance between your line and its best-fit circle, as a percentage of that circle’s radius. The best-fit circle comes from Kåsa’s algebraic least-squares fit, refined by Landau’s geometric iterations, and your stroke is resampled every 2 pixels first. Only one full turn is judged; any overlap past your start is trimmed.
What is a good score for drawing a circle?
On this test’s own scale, 96% or more means there is barely a pixel between your line and the true circle, over 90% looks round to anyone’s eye, and 80% is recognisably a circle with a bulge or flat side. Those tiers are a rough guide we set, not a norm drawn from other people’s circles.
Is there a scientific average for how round people draw circles?
Not for this measure. When we checked in October 2026 we found no published adult figures for a one-stroke circle’s deviation from its best-fit circle. Circle-drawing studies measure other things: Krabben and colleagues (2011), for example, had 20 healthy adults draw large circles above a table and scored roundness as an ellipse’s axis ratio.
What do shake and oval mean in my circle report?
Shake is the small, fast part of the straying — what remains after the slow bulges are smoothed over about 20° of the circle — and it reflects the slight tremor every hand has. Oval is the slow, two-lobed part: how egg- or lemon-shaped the circle came out, and which way its long axis lies.
Why didn’t my stroke count?
A stroke has to go at least 330° of the way round and be bigger than about a coin, a radius of 60 screen pixels. Anything shorter or smaller isn’t treated as an attempt, so it doesn’t use up one of your three tries; just draw again until you meet your starting point.
Can drawing a circle detect tremor?
Not this one. Clinicians do rate tremor from drawings, typically spirals and handwriting on paper, rated by trained raters — Bain and colleagues tested such ratings in 1993 — but a single circle drawn with a finger on a screen is not that test. The shake figure here is only a description of your stroke.
Where the numbers come from
The score is a measurement of your stroke against its own best-fit circle; there are no population norms for it, and the tiers are this site’s own. The site does not publish its own players’ data.