Circle Skirt Calculator
A circle skirt is one piece of fabric with a hole in the middle, and the hole has to be exactly as long around as the waist it hangs from, so its radius is the waist measurement divided by 2 pi. This calculator does that division on the first screen and then shows the rest of the pattern beside it: a 28 in waist on a full circle gives a 4.46 in waist radius, a 28.46 in hem radius on a 24 in skirt, a 56.91 in square to cut from, and 1.6 yd of 60 in goods. What it does differently is keep the allowances honest and the fullness in view. The seam allowance moves the cutting circle inward by exactly its own width and is never added at the hem as well, ease is added to the waist once before the division, and the same numbers are answered at all three fullnesses at once, so you can see that the half circle wants 8.91 in at the waist and the quarter circle 17.83 in before you cut anything. Work in inches with fractions such as 28 1/2 and 5/8, or switch to centimetres and the numbers convert with you: a 60 cm waist comes out at 9.55 cm.
waist 28 in fullness full circle length 24 in waist radius 4.46 in hem radius 28.46 in cut square 56.91 in fabric 1.6 yd at 60 in layout one piece
waist radius = 28 ÷ (2π × 1) = 4.46 in. Cut the waist circle at 4.46 in and the outer edge at 28.46 in, measured from the same centre point. Radii print to two decimal places, with the nearest eighth of an inch beside them for a tape measure. The fabric figure is an estimate for a plain layout with the straight grain running down the skirt, rounded up to the nearest tenth of a yard: add more for a print to match, a nap, or a prewash that shrinks.
The whole circle fits across 60 in goods: 56.91 in of 60 in goods, one piece, folded in four and cut once. Leave an opening in one side for the zip.
The same waist, three fullnesses
The waist measurement is spread over the fullness you pick, so a half circle needs twice the waist radius of a full circle and a quarter circle four times it. The fabric beside each one is that layout on the goods you entered.
Common questions
- How do I calculate the waist radius for a circle skirt?
- Divide the waist measurement by 2 pi, which is about 6.2832, and for a full circle that is the radius of the hole you cut. A 28 in waist gives 4.46 in, and a 60 cm waist gives 9.55 cm. Less fullness means the same waist is spread over less of a circle, so the division changes with it: divide by 2 pi times 0.5 for a half circle and by 2 pi times 0.25 for a quarter. The outer radius is that waist radius plus the finished length, so a 24 in full circle skirt is marked at 4.46 in and again at 28.46 in from the same centre point.
- What is the difference between a full, half and quarter circle skirt?
- The fullness is how much of a circle the waist opening is cut from, and it decides both the sweep of the hem and the size of the hole. On a 28 in waist the full circle waist radius is 4.46 in, the half circle is 8.91 in and the quarter circle is 17.83 in: less fullness means a bigger hole and a straighter, narrower skirt. Fabric does not always follow that order, and the calculator shows it rather than hiding it. On 60 in goods with a 24 in length the full circle fits in one piece at 1.6 yd, while the half circle has a 65.83 in straight edge that will not cross 60 in goods, so it is cut as two panels at 1.9 yd; the quarter circle takes 1.2 yd. The three rows under the readout answer all three at once.
- Do I add the seam allowance to the waist radius or take it away?
- Take it away. The waist radius is the finished measurement, so the allowance sits inside it: cut the circle smaller by the allowance and the seam falls back on the line you calculated. With a 4.46 in waist radius and a 5/8 in allowance, the cutting circle is 3.83 in. This tool keeps that separate from the finished figure, shows both, and never adds the waist allowance at the hem as well, which is the double count that makes a finished waist come out too big. A hem allowance works the other way and is added outside the finished edge.
- How much fabric does a circle skirt need?
- It depends on the outer radius and the usable width of your goods, so enter the width and the estimate follows the layout. A full circle whose diameter fits across the fabric is cut in one piece from a square, which is 1.6 yd for the 28 in, 24 in example on 60 in goods. When the full circle is wider than the fabric, it is cut as four quarter panels joined by four seams, and the same skirt takes 3.2 yd of 45 in goods. Pieces are laid with the straight grain running down the skirt rather than turned sideways, the figure is rounded up to the nearest tenth of a yard or metre, and goods narrower than one cut radius are reported as too narrow instead of guessed at.
- Should I add ease to the waist measurement?
- That is your call, and the ease field is there for it: whatever you enter is added to the waist once, before the division, so 28 in with 1 in of ease is worked as 29 in. Because the division is by 2 pi, an inch of ease only moves the radius by about 0.16 in, which is why measuring the waist carefully matters more than the ease does. Leave the field empty and no ease is added at all.
- Can I work in centimetres, or type fractions of an inch?
- Both. Fractions read the way you write them on a pattern, so 28 1/2, 28-1/2 and 5/8 all parse, and so does a decimal or a number with in or cm after it. Switching the units converts what you typed rather than relabelling it, so 28 in becomes 71.12 cm, and a goods width still sitting on the standard 60 in moves to the standard 150 cm rather than to 152.4, because a bolt width is a convention rather than a conversion. In inches the readout also prints the nearest eighth beside each radius for measuring against a tape.
- Does anything I type here leave my browser?
- No. The arithmetic runs in the page, there is no account and nothing is uploaded. Your last set of measurements is kept in this browser so the numbers are still there after a reload, and if storage is blocked the calculator still works, it simply opens on the worked example each time.
Exact geometry: the waist radius is the circumference divided by 2π, adjusted for the fullness you choose. Seam allowance and hem allowance are added only if you enter them.