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Proportion Eye

split lengths by eye — tick halves, thirds and ratios

round
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score
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best
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Judging a division without measuring it

Every answer here is a short tick drawn across the thing being measured, so the guess leaves your hand. The six items run in a fixed order: halve a bare segment, then find both thirds of it, then both thirds of a steep one, then a named fraction such as 5/8 measured from the left end, then the halfway point of a standing figure — the classic 7.5-head build, with an unlabelled head-unit ruler standing beside it while you guess — and then a midpoint again, so the round closes on the item beginners read best rather than on arithmetic. Each reveal draws the true divisions and reports your miss in both percent and pixels.

Halves are the cut the eye handles most reliably, which is why painters find the middle first and split again from there; thirds and an odd ratio like 5/8 are where that habit starts to wobble, and the steep segment removes the comfort of a level line to check against. The figure's head-unit ruler stays unlabelled while you decide, so the answer has to be seen before it can be checked. A tick drawn near the line is pulled onto it instead of being refused, undo stays live for 1.8 seconds after the last tick, and a reveal sits there until you tap it away.

What counts as close enough

A mark is graded on its distance from the true division, as a share of the length being divided. Inside 1% is perfect and 11% off is worth nothing. Both windows carry an absolute pixel floor, eased for pen, mouse or finger, which is why a 215px phone segment is not held to a 2.15px perfect zone while a desktop is allowed 4.5px. An item scores the mean of its own marks, the round scores the mean of its six items, and the HUD keeps that mean running as you go. No model is involved anywhere in that: the drill drew the segment, so the true division is a fraction of a length it already knows, and the whole score is arithmetic on the gap between that and your tick.

More observation drills: Negative Space · Anatomy Spot · Gesture Capture · the whole catalogue