Perception · Test

Size Comparison

Which shape is larger? Thirty judgements, from obvious to very close.

No account. No tracking. Your results stay with you.

Ready

Which shape is larger?

Choose with ← → keys, a click or a tap. Thirty judgements, from obvious to very close.

Needs to compare two shapes visually. Answer with ← → keys, clicks or taps.

How this is measured

Two shapes of the same kind appear, each randomly rotated and nudged. Choose the larger one — with ← and → keys, a click or a tap. The difference in size starts at 20% and steps down through 12%, 8%, 5% and 3% to 2%, five judgements at each level.

Shapes, sides and rotations are random every time; the difficulty schedule is fixed, so your accuracy can be compared from one attempt to the next.

Scoring

score = correct ÷ 30 × 100 difference = (larger side − smaller side) ÷ smaller side

Accuracy per level is shown so you can see where it gets hard. Response time is recorded but secondary. No answer within 5 seconds counts as wrong.

What can affect the result

Screen size and pixel density (2% of a small shape may be a single pixel).
Rotation and shape: triangles are harder to judge than circles.

What this does not mean

This is an interactive challenge, not lab-grade psychophysics, and it doesn't measure eyesight.
It is not a medical, psychological, neurological or hiring assessment, and it cannot diagnose or screen for anything.

Your results stay here

The test runs entirely in this browser tab. Results are saved only in this browser's local storage so you can compare with yourself — never uploaded, never tracked. You can clear them any time.

Size Comparison

Size Comparison test

How this is measured

Scoring

What can affect the result

What this does not mean

Your results stay here

Related tests

How this is measured

Scoring

What can affect the result

What this does not mean

Your results stay here