Draw a Perfect Circle

How steady is your hand? Draw a perfect circle with your finger or mouse and this circle game measures how round it really is, live, as you draw. Most people land in the 70s and 80s. Can you break 95%?

How to play Draw a Perfect Circle

• Around the dot: press anywhere away from the dot and draw one full loop around it without lifting. The score updates as you go and the attempt ends automatically when you get all the way round.
• Freehand: draw a circle anywhere on the board. When you lift your finger or mouse, the best-fitting circle is worked out and your drawing is compared with it.
• Your line turns from green to red where it drifts away from a true circle, so you can see exactly where it went wrong.
• The score is how close your line stays to one radius all the way round: 100% is a mathematically perfect circle. Circles that are too small, unfinished or that touch the dot don’t count.
• Your best score for each mode and your last ten tries are saved. Use Share score or Save score card to challenge a friend.

Controls

• Touch or mouse: press, draw one loop, release
• R or Enter — clear the board and try again

Tips

• Move your whole arm, not just your wrist. Big circles from the shoulder are smoother.
• Go at a steady, medium speed. Very slow lines wobble; very fast ones overshoot.
• Keep your eyes on the dot rather than the tip of your finger, and aim for the same distance all the way round.
• On a phone, rest the edge of your hand on the screen and turn the phone a little as you draw.

FAQ

How is the perfect circle score calculated?

Your line is sampled at evenly spaced points. We measure how far each point is from the average radius and turn the average error into a percentage. An average wobble of about 3% of the radius gives a score near 90%.

Can anyone draw a perfect circle?

Not by hand. Even very skilled artists drift a little, so 100% is out of reach, but scores above 95% are possible with practice.

What is a good score?

Most first attempts land between 70% and 85%. Above 90% is excellent, and above 95% is exceptional.

Why did it say “Draw a full circle”?

You lifted your finger before going all the way round. Your loop has to cover the full 360 degrees to be scored.