Drill 03Ellipse inside a plane
How to draw ellipses
Draw one ellipse inside the box. Find out whether its degree, its angle or its evenness is what let it down.
Measures your line, not your drawingRuns on your deviceFree and unlimitedWant a real drawing checked?
Draw one ellipse that fills the box. Two laps, without lifting.
How it works
What it can name
The faults, drawn
A percentage on its own tells you nothing you did not already know. These are the separable problems the measurement identifies — each with a different fix, which is the whole reason for telling them apart. Every example below is a real stroke, generated by the same code that tests the engine.
Too round
The commonest ellipse error by far — the eye knows the real shape is a circle and quietly corrects toward one.
Too narrow
The hand travelled further along the long axis than the short one allowed for.
Tilted
The long axis follows your arm’s preferred sweep rather than the plane’s.
Pinched end
One end tightens where the hand is deepest into its reach and starts to decelerate.
Tremor
Shake on top of a shape that is otherwise right. Opposite fix to a pinched end.
Not closed
One lap leaves nothing to close against. This is exactly what drawing through solves.
Drifting laps
Drawing through only helps when every lap runs the same path.
Too small
The right shape, but not bounded by the box it belongs to.
Two tools, two questions
What this drill looks at
This drill · your line
Measures the stroke itself — how round, how straight, how evenly spaced, how far off the mark, and how the hand moved while it drew.
The number is arithmetic. The finding is not: which fault a set of measurements adds up to, and which fix it takes, is how drawing has been taught for a century. The instrument locates it; the teaching names it.
- Instant, exact, and the same answer every time
- Free and unlimited — it costs nothing to run
- Runs on your device; your drawings never leave it
- Cannot tell you whether the drawing works
Rate My Sketch · your drawing
Coach Luna checks a real drawing — a photo of your sketchbook or a screenshot — and marks the corrections onto the image itself.
She measures technique against what you were drawing: proportion versus your reference, shading, the joins. Never your creativity, your style or your subject — those are not hers to grade.
- Five technique scores, and the single fix to make first
- Three free every day, no account needed
- Generates nothing and never redraws your work
- Slower, and needs something real to look at
The two scores are different measurements and are not meant to agree. A circle can be geometrically excellent inside a drawing that does not work, and a drawing can work with shaky circles all through it. Use the drills to build the hand, use the critique to find out what the drawing needs next, and when you want the rest taught properly — construction, form, light, composition — that is what the Sketching Essentials course is for.
Is this the one you need?
Take all 7 drills and get a profile
About 5 minutes. It names your weakest skill and sends you to the drill that measures exactly that.
How the number is made
What the score actually measures
Degree
asin(minor / major)21% of the scoreHow squashed your ellipse is, compared with what the plane asks for. 90° is a circle head-on; small numbers are a circle seen at a shallow angle.
Alignment
fitted axis − plane axis16% of the scoreHow far your long axis is rotated out of the box. Wraps at 90°, because an axis has no direction.
Shape
harmonics 3–5 of radial error13% of the scoreSmooth deviation from a true ellipse — one end pinched, one end fat. Orders 0–2 are absorbed by the fit itself, so what is left is genuinely shape.
Steadiness
residual after harmonic 511% of the scoreWhatever is left once the shape is accounted for. That is tremor, and it needs the opposite advice from a shape problem.
Fill
fitted axes / plane axes10% of the scoreWhether the ellipse touches all four edges, comes up short, or spills over.
Tempo
last lap’s speed ÷ first lap’s6% of the scoreWhether the second lap was swung or traced. Everything else here reads the shape, and a lap drawn slowly on top of the first lands beautifully on it — so a second lap at half the speed of the first produced a geometrically perfect ellipse and nothing to say about it. Drawing through is meant to be the same movement twice; a traced second lap is the hand following a line it can already see. A uniformly slow attempt scores full marks here, because that is a different fault and has its own name.
Placement
distance from your centre to the plane’s centre ÷ plane size9% of the scoreWhether the ellipse sits where the plane is. An ellipse of exactly the right degree and shape, drawn off to one side, is not the ellipse the plane asked for — and this is the error that survives longest, because it is invisible while you are looking at the curve rather than at the box around it.
Closure
distance from your first point to your last ÷ radius6% of the scoreWhether the second lap came back to where the first began. Two laps make this harder and more informative than it is on a circle: the pen has to arrive back at a point it left a full turn ago, with nothing to aim at.
One go
stops counted along the stroke, over the length of it8% of the scoreWhether the ellipse was drawn or assembled. Every other measure here reads the shape, and a stroke that stops and re-aims can come out geometrically perfect — so a ellipse drawn in fourteen separate stops could score 99 while the page told you it had been steered round in pieces. It counts stops rather than wobbles in the speed, because a stop is something the hand did and a wobble is partly the tablet: on ninety correct drawings across four levels of capture noise and three report rates, the stop count is zero every time.
Everything is measured in the ellipse’s own space: we fit the ellipse, then map your stroke through the inverse transform so it becomes a circle. An ellipse IS a circle under an affine transform, so all the roundness machinery applies unchanged — which is why "one end is pinched" can be stated at all. Every threshold, and the evidence behind it.
The technique
Draw a better ellipse
- 01
Read the box before you draw
Decide how squashed the ellipse has to be first. Almost everyone draws ellipses rounder than the surface they sit on, because the eye knows the real shape is a circle.
- 02
Aim the long axis
Trace the box’s long axis in the air a couple of times. An ellipse drawn without aiming lands on your arm’s preferred sweep, not on the plane’s.
- 03
Draw through, at least twice
Two laps without lifting. The second closes the first, and you never have to aim at your own starting point.
- 04
Do not slow down at the ends
The far end is where the hand is deepest into its reach, and where everyone hesitates. That hesitation is exactly what pinches the curve.
Why an ellipse is harder than a circle
A circle has one number to get right. An ellipse has three — how squashed it is, which way it points, and whether both ends curve alike — and they fail independently, so an ellipse can be wrong in ways that look identical from a distance.
It is also the shape with nowhere to rest. A straight line has a settled direction and a circle has constant curvature, but an ellipse changes direction continuously and unevenly: fast through the ends, slow along the sides. There is no safe place to pause and re-aim, so every hesitation becomes a corner.
That is why it is the shape most worth measuring. Wheels, cups, bottle openings, eye sockets, the top of a mug — every circular thing seen at an angle is an ellipse, and getting its degree wrong is the single most common reason an otherwise careful drawing looks off.
Why we give you a box
A bare ellipse cannot be wrong. Any oval is a valid ellipse, so scoring one on its own would mean inventing a target and then marking you against it.
A plane fixes that. The box supplies a degree and an axis, so "too round" and "rotated out" become measurements rather than opinions. It is also how the exercise is taught: an ellipse belongs to a surface, and drawing one without knowing which surface is the habit the drill is trying to break.
We deliberately do not show the ellipse itself, only the box. Tracing an outline measures nothing.
When you have got it
Three in a row above 80 with no named fault, drawn through two laps in about a second. Then change the box: try a narrow 15° plane and a nearly-round 70° one, and notice which direction your error runs — almost everyone is consistently too round, and knowing your own bias is worth more than any single score.
Questions
What does "degree" mean here?
How squashed the ellipse is, as an angle: asin(minor axis ÷ major axis). A 90° ellipse is a circle seen head-on; a 20° ellipse is a circle seen at a shallow angle. It is the standard way to talk about ellipses in drawing because it maps directly onto how far the surface is tilted away from you.
My ellipse looks fine but scores badly. Why?
Check the breakdown rather than the total. Almost always it is the degree: an ellipse that is a perfectly good shape can still be the wrong shape for that box, and that is the error that makes drawings look off.
Why does it want two laps?
Because one lap gives you nothing to close against, and aiming at your own starting point is far harder than simply carrying on past it. Drawing through is also how you find out whether your laps agree — if they do not, the pivot moved.
Does drawing through count against me for being messy?
No. Closure is only checked on a single-lap attempt, and consistent laps earn a strength rather than a penalty. What is measured on a multi-lap attempt is whether the laps sit on each other.
Why is one end of my ellipse always pointier?
The far end is where your hand is deepest into its reach, so the arm decelerates and the curve tightens before it can come back round. Keeping the speed constant through the ends is the fix, and it is easier at speed than slowly.
Why is there no eraser?
Because the ellipse you drew is the measurement, and tidying the bad half of it would change the reading without changing your drawing. Undo starts the stroke over; attempts are unlimited.
Is my drawing uploaded?
No. The ellipse fit, the harmonic decomposition and every number on this page are computed in JavaScript in your browser. Nothing is sent anywhere and no model is involved.
Next drill
Divide by eye
Mark the middle of every bar. Short ticks, by eye — no measuring.
Drew something real?
Rate My Sketch
These drills measure geometry. For a drawing with a subject in it, Luna scores five technique dimensions and marks the corrections on your image.