How to draw ellipses
Draw one ellipse in the box. Note the degree, angle and evenness of the shape.
The classic foreshortened plane. Minor axis about half the major.
Draw one complete ellipse to fill the box. Make two full laps without lifting.
The technique
Draw a better ellipse
4 steps
- 01
Read the box before you draw
Work out how squashed the ellipse needs to be before drawing. Compare the box’s short dimension with its long one. Use that relationship to plan the loop instead of automatically making it circular.
- 02
Aim the long axis
Rehearse along the box’s long axis in the air a few times, then rehearse the whole ellipse around it. This helps you keep the loop pointing with the box rather than following a different direction.
- 03
Draw through, at least twice
Two laps without lifting, as the second lap immediately follows the first, and thus there is no need to re-target.
- 04
Do not slow down at the ends
Keep the movement flowing through both rounded ends. If one end pinches, rehearse that turn before your next attempt. The shape does not prove that you reached too far or hesitated.
How it works
What it can name
The faults, drawn
These percentages can mean nothing by themselves. Instead, each problem has its own fix. The examples below are all real strokes that I generated with the same code that I used to test the engine.
Too round
The ellipse is rounder than this guide asks for. Compare its long and short dimensions with the box before drawing again.
Too narrow
The ellipse is flatter than the guide. Give the short direction more room while keeping the long direction inside the box.
Tilted
The ellipse's long axis points away from the guide's long direction. Rehearse the intended slant before drawing again.
Pinched end
One end tightens into a point or pinch. Rehearse a rounded turn at that end before trying the full loop.
Tremor
Small uneven changes interrupt the ellipse's curve. Aim for a steady pass while keeping its overall width and height in mind.
Not closed
The loop is incomplete or its join is open. Follow the two-lap demonstration without lifting, then check that the outline closes.
Drifting laps
The laps drift apart. Aim both passes along the same planned ellipse, without trying to trace every wobble from the first.
Too small
The ellipse sits outside the intended box or misses its contact areas. Check the placement and size against the guide.
How the number is made
What the score actually measures
Degree
asin(minor / major)19% of the scoreHow squashed your ellipse is compared with the plane’s target. Here, 90° means a circle; lower degrees describe progressively narrower ellipses. The degree comes from the ratio of the fitted axes.
Alignment
fitted axis − plane axis15% of the scoreHow far the ellipse’s long axis is rotated away from the box’s long axis. An axis points both ways, so the difference is measured as the smaller angle between the two lines, from 0° to 90°.
Shape
harmonics 3–5 of radial error12% of the scoreThe smooth deviation of the actually drawn ellipse from the true, perfect shape of an ellipse. Note that the errors of order 0 through 2 are absorbed by the fit itself, so the remaining error is actually due to the shape of the ellipse.
Steadiness
residual after harmonic 510% of the scoreSmall irregularities left after the larger shape variations have been accounted for. They can reflect your stroke or device capture; the measurement alone cannot diagnose tremor or prescribe the opposite of shape advice.
Fill
fitted axes / plane axes10% of the scoreWhether the ellipse fills the plane or not.
Tempo
last lap’s speed ÷ first lap’s5% of the scoreHow the last lap’s speed compares with the first lap’s speed. Drawing through asks you to repeat the movement, rather than slowly trace over a visible line. A much slower second lap affects this term. An evenly slow attempt is a different issue and can receive separate feedback.
Placement
distance from your centre to the plane’s centre ÷ plane size8% of the scoreWhether your ellipse sits in the middle of the plane. A good shape drawn off to one side still misses the target. Check the space around the ellipse as well as the curve itself.
Laps drawn
laps short of the two asked for8% of the scoreWhether you drew the two laps requested. Stopping a lap short affects the technique score; the ellipse you did draw is still measured for degree, alignment and fill. The second lap is another turn around the shape, not the second half of one turn.
Closure
distance from your first point to your last ÷ radius6% of the scoreHow close your ending point comes to your starting point once you have drawn the requested laps. Stopping before enough of the second lap is drawn is handled as missing lap coverage, so it is not simply counted again as a closure gap.
One go
stops counted along the stroke, over the length of it7% of the scoreWhether you kept moving or built the ellipse with repeated stops and re-aims. A shape can look even despite those stops, so this term uses stroke timing. Small speed fluctuations from capture are not all treated as stops, but the measurement cannot guarantee a zero count on every device.
To score this, we need to first decide how squashed your ellipse is, then we map your line through the inverse of that transformation so it becomes a circle, and we score it using the roundness machinery as if it were a circle. So “one end is pinched” can actually be scored for. Every threshold, and the evidence behind it.
What an ellipse inside a box asks you to control
An ellipse inside a box gives you several things to control: how squashed it is, which way it points, and whether the two ends curve evenly. These can vary independently, so similar-looking attempts can need different adjustments.
The direction changes all the way round an ellipse, with tighter turns at the ends of its long axis. Try to keep the movement flowing through those turns. Stopping to patch an edge can leave a bump or corner, although a pause does not always leave a visible mark.
Ellipses are useful for circular rims and wheels seen at an angle: a cup opening, bottle top or wheel can all need this shape. Getting the width and orientation to fit the object helps it read clearly. It is one part of construction drawing, not a measure of every feature of an object.
Why we give you a box
An ellipse on its own can still be uneven or poorly closed, and not every oval is a true ellipse. What it lacks is a target for its degree, size and direction. The box gives this exercise those extra relationships to measure.
Now add a plane to that set-up. The box allows us to set a degree and an axis. So rather than an exercise in drawing ‘ovals’, we now have an exercise in which we can determine whether our drawn oval is too round or if it has been rotated out of the box. This is how the ellipse drawing exercise is normally taught. The ellipse is a shape that belongs to a surface.
The target guide is a box, rather than an ellipse to trace. A demonstration can show the movement, but on your attempt you work out the ellipse that fits the box. You are drawing its outline, not shading in a surface.
When you have got it
Try for three in a row above 80 with no named fault, using two continuous laps at a comfortable pace. Then use the plane selector to try the narrow 15° box and the nearly round 70° one. Watch whether your own attempts tend to be too round or too narrow rather than assuming everyone has the same bias.
Questions
What does "degree" mean here?
Here, degree is calculated as asin(minor axis ÷ major axis). A 90° ellipse is a circle, while 20° describes a much flatter ellipse. In the simplified view used by this drill, it relates a circular surface’s tilt to how squashed its outline appears.
My ellipse looks fine but scores badly. Why?
Look at the score breakdown. A smoothly drawn ellipse can still be too round, too narrow or rotated for its box. The named feedback helps you choose an adjustment; degree is one possible issue, not automatically the main one.
Why does it want two laps?
Two laps let you practise repeating a continuous movement without stopping to patch the first loop. They also let you compare how the loops sit together. If they drift apart, rehearse the shape again; the drift does not prove that a particular pivot or joint moved.
Does drawing through count against me for being messy?
Drawing through the requested two laps is part of the exercise, so overlapping those laps is expected. The engine checks lap coverage, timing and closure as well as shape. A missing lap or an ending that falls short can still affect the result; simply drawing a second lap is not the fault.
Why is one end of my ellipse always pointier?
A pinched end may come from tightening or correcting the turn as you draw it. Rehearse the full loop, then try to carry the movement smoothly through both ends. Use a comfortable pace; the curve alone cannot tell us how far your hand reached or whether faster will fix it.
Can I erase or start again?
You can use the eraser to remove unwanted ink; the engine measures the remaining strokes. For the two-lap practice, a fresh attempt is often easier to learn from than a heavily patched one. Use Undo or clear the canvas when you want to start again. Attempts are unlimited.
Is my drawing sent to an AI model?
The ellipse fit, harmonic decomposition and scoring run in JavaScript in your browser, using the recorded coordinates and timing. The same stroke and scoring settings give the same result. This exercise does not send your drawing to an AI model.
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