Drafting a Circle Skirt and Calculating the Radius

A circle skirt is cut so that the waist edge is a circular arc and the hem is a larger concentric arc. The waist sits flat against the body while the extra length around the larger hem circle has nowhere to go but fall into folds, producing the skirt's characteristic swirl. The more of a full circle the skirt uses, the more fabric hangs at the hem and the fuller it is.

Because there is no dart or gather, the fit at the waist depends entirely on cutting the inner arc to exactly the right radius. Too large and the skirt slips off; too small and it will not close. This is why the radius calculation is the heart of the draft.

The waist edge is a circle, so its length equals two times pi times the radius. To find the radius for a full circle skirt, divide the waist measurement by two pi, which is about 6.28. A waist of 72 centimetres gives a radius of 72 divided by 6.28, roughly 11.5 centimetres. You draw that radius from a center point to mark the waist arc.

For a half circle skirt the waist arc is only half a circle, so it must fit the same waist over half the arc; divide the waist by pi instead, about 3.14, giving a larger radius. For a quarter circle, divide by half of pi. The smaller the fraction of a circle, the larger the radius and the less fullness at the hem.

• Full circle: waist divided by 6.28; maximum flare and the most dramatic hem waves.
• Half circle: waist divided by 3.14; moderate flare, more economical with fabric.
• Quarter circle: waist divided by 1.57; gentle A-line flare, least fabric.
• Fuller circles need more fabric width and often must be pieced or cut in panels.
• Less-than-full circles reduce bias drop and are easier to hem evenly.

1. 1.Calculate the waist radius from the appropriate divisor for your chosen circle fraction.
2. 2.From a corner point, draw the waist arc at that radius.
3. 3.Add the desired skirt length outward from the waist arc to mark the hem arc.
4. 4.Cut along both arcs to produce the skirt piece.
5. 5.Add seam allowance at the waist and side seams, and a narrow hem allowance.

A circle skirt crosses every grain direction, so parts of the hem fall on the bias and stretch downward over time. This bias drop makes the hem uneven if you finish it immediately. Hang the cut skirt for at least twenty-four hours, then re-mark the hem level from the floor before finishing, so the settled length is even all the way around.

Keep the hem allowance narrow, because a wide hem cannot turn up smoothly on a curved edge without puckering. A rolled or narrow machine hem, or a bias-bound edge, follows the curve far better than a deep folded hem.

A circle skirt pattern is defined by its arcs and its center point, which digitize cleanly as precise curves. Minerva Patterns supplies circle and part-circle skirts as DXF AAMA, PLT and PDF, drafted to an individual waist measurement so the inner radius fits exactly, with the grainline and hem allowance set for even bias drop.

The beauty of the circle skirt is that once you internalize the radius formula, the whole garment is on demand: choose the fullness, compute the radius, add the length, and the geometry does the rest.