Draw a Straight Line is a free online precision drawing test that challenges you to draw the straightest possible line between two points using only your mouse or finger. Across 5 rounds at different angles — horizontal, vertical, and diagonal — the test measures your average pixel deviation from the ideal line. It is harder than you think.
Each round places a green start point and a red end point on the screen at a different angle. You click or tap the start point, then draw freehand to the end point. The test samples your drawn path every 3 pixels and calculates the perpendicular distance from each point to the ideal straight line. After each round, you see your score, average deviation, and maximum deviation, along with a visual overlay comparing your line to the perfect one.
The test measures the average perpendicular deviation of your drawn line from the ideal straight line connecting the two points. It calculates the distance from each sampled point on your drawn path to the perfect line, then averages those distances. Lower average deviation means a straighter line and a higher score.
A total score of 375 or above out of 500 earns the "Steady Hands" rating. Scoring 450+ is rated "Human Ruler" — meaning your average deviation was under 3 pixels per round. Most players score between 200 and 350 on their first attempt.
It is extremely difficult to draw a perfectly straight line freehand. Even with a steady hand, micro-movements in your muscles cause small deviations. This test quantifies exactly how straight your line is by measuring pixel-level deviation across 5 rounds at different angles.
If you enjoyed this, try these: Perfect Circle · Steady Hand · Pixel Perfect · Balance Point
Last updated: March 2026 · whatifs.fun — Free interactive games, experiments & simulations