Draw a circle freehand in one stroke. Get scored on how close it was.

How the score is calculated

The tool takes the fixed centre dot as the origin, measures the distance from it to every point you drew, and looks at how much those distances vary. A perfect circle has zero variation; the more your radius wobbles, the further the score drops. If your radius at the end of the loop differs from where you began, that difference counts as wobble too.

Why humans are bad at this

Freehand circles come out as ovals because the joints doing the work move in arcs, not circles. Drawing from the wrist gives you a flattened ellipse tilted toward your forearm; the elbow adds a second arc in another direction. People who score well are usually drawing from the shoulder, moving the whole arm as one unit, which is exactly what art teachers mean by "draw with your shoulder, not your fingers".

Things that actually help

Go fast — slow strokes let you correct mid-way, and every correction shows up as a bump in the radius. Start at the top or bottom rather than the side. Keep the circle large; small circles concentrate error. And if you are on a trackpad, expect a lower ceiling than a mouse or a touchscreen: the gesture is too short to smooth out.

The Giotto story

Legend has it that when the Pope's envoy asked Giotto for a sample of his work, the painter dipped his brush and drew a perfect circle freehand in a single stroke. Whether or not it happened, "Giotto's O" became shorthand for effortless mastery — and it is why a freehand circle still feels like a test of skill rather than a party trick.

How a round works

What counts as a failed attempt

Passing within 24 pixels of the centre dot cancels the stroke with a "draw bigger" message. Taking longer than 8 seconds cancels it as too slow. Lifting your finger before the loop is complete cancels it too: "go all the way around" if you covered less than half a turn, "so close" if more. Failed attempts are not recorded and there is no limit on retries.

The exact formula

Every point of your stroke gives one radius, the distance from the centre dot. The tool averages those radii, then averages how far each one strays from that mean (the mean absolute deviation). Accuracy = 100 − (mean absolute deviation ÷ mean radius × 100). Because it is a ratio, the size of your circle does not change the score by itself; only how constant the radius stayed matters. While drawing, each segment is coloured lime when its deviation is under 4 percent, yellow under 10 percent and pink beyond that, so you can see exactly where the wobble happened.

Grades

Leaderboard and sharing

The global leaderboard is the top 10 by accuracy, and a nickname of up to 12 characters is all it takes to enter. Your personal best is stored in the browser and shown on the title and result screens. The share link carries 72 radius samples taken every 5 degrees, so a friend who opens it sees your actual shape redrawn, along with your score as the mark to beat.

Does drawing bigger help?

Not directly. The formula is a ratio, so size alone does not add points. But a small circle turns ordinary hand tremor into a large fraction of the radius, which hurts. Use most of the pad while keeping the loop quick enough to finish inside 8 seconds.

Does direction matter?

No. Clockwise and anticlockwise are scored identically and you can start at any angle. Only the accumulated rotation is tracked, so the round ends the instant a full turn is complete, wherever that happens to be.

Is 100% possible?

It would need an identical radius at every point, which a hand cannot do. Anything from 97% up already earns the top grade, Human compass, and since scores are kept to one decimal place, leaderboard positions are often decided by a tenth of a percent.

Related tools