Craft & sewing Australia
Circle Skirt Calculator
Enter your waist measurement and the finished length. The calculator returns the radius to mark from, how much fabric to buy at Australian bolt widths, and whether it will fit in one piece or needs a seam.
Free, no signup Runs in your browser
Measure where the skirt will actually sit
Waist seam to hem
2 cm is typical; 0 for a zipped waistband
Waist radius to mark
โCut radius (to hem)
โ
Hem sweep
โ
Fabric to buy
โ
Layout
โ
How do you calculate a circle skirt radius?
Divide the waist measurement by 2ฯ for a full circle skirt โ that radius is the waist opening you cut out. For a 70 cm waist that is 70 รท 6.2832 = 11.1 cm. Half and quarter circle skirts spread the same waist length over less of a circle, so their radii are 22.3 cm and 44.6 cm.
The two radii, and which one you actually mark
There are two circles to draw, and they are measured from the same centre point.
The waist radius is the small one โ the hole. It comes straight from the circumference formula, because the waist opening has to have a circumference equal to your waist plus ease.
The cut radius is the big one: waist radius plus the finished length plus the hem allowance. Everything between the two circles is skirt.
The mistake that ruins fabric is marking the length from the centre point rather than from the waist line. That produces a skirt shorter than intended by the whole waist radius, and there is no fixing it after the cut.
Ease, and where the skirt sits
Ease is the extra room beyond your actual measurement. Two centimetres is comfortable for a skirt that pulls on over the hips or sits under a waistband with a zip.
What matters more is where you measured. A skirt sitting at the natural waist and one sitting on the hip need different measurements, and the difference is often ten centimetres or more. Measure at the height the finished skirt will sit, wearing whatever will go underneath, rather than at the narrowest point of your torso.
How this is calculated
A circle skirt is a doughnut. The waist is the hole in the middle, and the length is how far the fabric extends beyond it.
waist radius = (waist + ease) รท (2ฯ ร fraction)cut radius = waist radius + length + hem allowancehem sweep = 2ฯ ร cut radius ร fractionfabric width needed = 2 ร cut radius (for a full circle cut in one piece)
The fraction is 1 for a full circle, 0.5 for a half and 0.25 for a quarter. Because the same waist measurement is spread over less of a circle, a half circle skirt's waist radius is twice a full circle's, and a quarter circle's is four times.
That has a consequence people meet at the cutting table: less fullness means a larger radius, which means a wider piece of fabric to cut it from. A half circle skirt is not automatically the economical option.
A worked example: a 70 cm waist, knee length
A full circle skirt for a 70 centimetre waist, finished at 60 centimetres, with 2 cm of ease and a 3.5 cm hem and seam allowance, cut from 150 cm fabric.
- Waist plus ease72 cm
- Waist radius โ 72 รท 6.283211.5 cm
- Add length and hem allowance11.5 + 60 + 3.5
- Cut radius75 cm
- Fabric width needed โ 2 ร 75150 cm
- Hem sweep โ 2ฯ ร 75471 cm
Mark an 11.5 cm waist radius and a 75 cm cut radius. It fits 150 cm fabric in one piece โ just โ needing 1.5 metres.
Fitting in one piece at exactly the bolt width leaves no margin for a fabric that has been cut off-grain at the shop. An extra 20 centimetres costs little and removes the problem.
Letting the bias hang before hemming
A circle skirt crosses every grain direction as it goes round. Where the fabric is on the true bias โ roughly the diagonal quarters โ it stretches under its own weight, and it keeps stretching for a day or two after cutting.
Hem it immediately and those sections drop later, leaving a hem that dips unevenly. The standard fix is to hang the cut skirt on a hanger or a dress form for 24 to 48 hours, then trim the hem level while it is hanging. On a heavy fabric or a long skirt, give it longer.
The drop is real and often several centimetres on a long skirt in a drapey fabric. It is the most common reason a home-sewn circle skirt hangs unevenly.
What this calculator does not do
- Assumes a fabric with no directional print or nap โ a one-way design needs more metres
- Does not include a waistband, facing or pockets in the fabric estimate
- Assumes fabric that will not shrink; wash and dry before cutting if it might
- Very long skirts on narrow fabric need piecing, which adds seams the estimate does not model
Common questions
How much fabric do I need for a circle skirt?
It depends on the cut radius and the bolt width. A full circle at knee length on a 70 cm waist needs about 1.5 metres of 150 cm fabric if it fits in one piece, and roughly double that if the cut radius exceeds half the bolt width and it has to be cut in halves.
What is the difference between a full, half and quarter circle skirt?
How much of a circle the fabric covers, which sets how much it flares. A full circle has the most sweep and uses the most fabric. A quarter circle is closer to an A-line. All three use the same waist measurement, so the smaller fractions need a proportionally larger waist radius.
Do I add seam allowance to the waist radius?
Subtract rather than add โ the waist seam allowance sits inside the circle you cut. Most patterns handle this by cutting the waist hole slightly small and trimming after the waistband is attached, which is far more forgiving than cutting it large.
Why does my hem hang unevenly?
The bias sections have stretched. Hang the cut skirt for a day or two before hemming, then trim it level while it is hanging on a form or a hanger.
Can I cut a circle skirt on the fold?
Yes, and for a full circle you usually must. Fold the fabric into quarters, mark both radii from the folded corner, and cut through all layers. That corner is the centre of the circle.
Where these numbers come from
- Wolfram MathWorld โ circumference and radius of a circle Fixed geometry, nothing to go out of date
Method last reviewed 2026-10-28 This calculator uses fixed rules rather than rates that change, and its method is re-checked against the sources above at least once a year. Out of date? Tell us and we will fix it.
Related AU calculators
Surd simplifier
Simplify any surd to its lowest form, with each step of the working shown.
Open calculator Maths & geometryCylinder volume
Volume from radius or diameter and height, converted to litres and cubic metres.
Open calculator PetsDog due date
Whelping date range from the mating date, with the vet checks along the way.
Open calculator