How do you calculate the waist radius for a circle skirt?

Divide your waist by 2 × π (about 6.28) for a full circle, by π for a half circle, or multiply it by 2 and divide by π for a quarter circle. Then subtract the seam allowance to get the radius you cut. For a 28 inch waist and a full circle, that is about 4½ inches at the seam line and about 3⅞ inches to cut.

How much fabric do I need for a circle skirt?

It depends on the skirt length and the fabric width. With a 28 inch waist, a 22 inch length and 5 percent for shrinkage, a full circle needs about 1⅝ yards of 58 to 60 inch fabric, or about 3¼ yards of 44 or 54 inch fabric, because there it has to be cut in two halves. A half circle takes about 1⅞ yards and a quarter circle about 1¼ yards on any of these widths.

What is the difference between a full, half and quarter circle skirt?

A full circle skirt has the most swing: laid flat, the hem is a complete circle. A half circle skirt is less full, and a quarter circle skirt is the slimmest, close to an A-line shape. The smaller skirts do not always save fabric: for the same waist, their waist radius is bigger, so their hem circle is bigger too. They save the most when a full circle would have to be cut in two halves.

Can a circle skirt have an elastic waist?

Yes. Enter the measurement the skirt must pass over, usually your hips, as the waist. The skirt then pulls on, and an elastic waistband gathers it in to fit your waist.

Why is my circle skirt hem uneven?

Parts of a circle skirt hang on the bias, the diagonal of the fabric, and those parts stretch more than the rest. Hang the sewn, unhemmed skirt for a day, then try it on, mark the hem level from the floor, trim and hem it.

Circle Skirt Calculator: Waist Radius and Fabric (Free)

Circle skirt calculator

How the circle skirt calculator works

A circle skirt is a ring of fabric. The inner edge of the ring is the waist and the outer edge is the hem, so the whole pattern comes down to two circles drawn from the same center point. The waist circle must measure your waist all the way around, which is why the first step divides by π.

Full circle: waist radius = waist ÷ (2 × π)Half circle: waist radius = waist ÷ πQuarter circle: waist radius = waist × 2 ÷ πWaist cutting radius = waist radius − seam allowanceHem cutting radius = waist radius + skirt length + hem allowance

For the fabric, the calculator checks how the skirt fits across the width of your fabric, keeping 1 in of the width for the selvages (the finished edges of the fabric). A full circle fits in one piece when it is no wider than that, and the fabric length is then twice the hem radius. If it is wider, the calculator plans two half circles cut one after the other, which takes four hem radii of fabric length. A half circle needs one hem radius of length when it fits across the width, or two when it is laid along the selvage. A quarter circle needs one hem radius. Then it adds the shrinkage and rounds up to the next ⅛ yard.

Worked example. A full circle skirt for a 28 in waist, 22 in long, with a ⅝ in waist seam allowance, a ½ in hem and 5 percent shrinkage. The waist radius is 28 ÷ 6.283 = about 4½ in, so you cut the waist circle at about 3⅞ in. The hem radius is about 4½ + 22 + ½ = 27 in, so the circle is about 54 in across. That fits on 58 to 60 in fabric in one piece, and 54 in plus 5 percent rounds up to 1⅝ yd. On 44 in or 54 in fabric it does not fit, so you cut two half circles and need 3¼ yd.

Draw both circles from the same corner of the folded fabric with a tape measure: hold the zero end at the corner and mark the radius every few inches as you swing it around. Parts of the waist edge are on the bias, the diagonal of the fabric, and stretch easily, so stay-stitch it (a line of stitching just inside the seam allowance) right after cutting. Let the sewn, unhemmed skirt hang for a day before you level and hem it.

Circle skirt waist radius chart

Waist radius at the seam line, before seam allowance
Waist	Full circle	Half circle	Quarter circle
24 in	3⅞ in	7⅝ in	15¼ in
26 in	4⅛ in	8¼ in	16½ in
28 in	4½ in	8⅞ in	17⅞ in
30 in	4¾ in	9½ in	19⅛ in
32 in	5⅛ in	10⅛ in	20⅜ in
34 in	5⅜ in	10⅞ in	21⅝ in
36 in	5¾ in	11½ in	22⅞ in
38 in	6 in	12⅛ in	24¼ in
40 in	6⅜ in	12¾ in	25½ in

Subtract your seam allowance from these numbers to get the radius you cut. Radii are rounded to the nearest ⅛ in.

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