# How do I cut a circle skirt?

Computes the waist radius, the outer radius, the hem circumference and the fabric rectangle for a full, 3/4, half or quarter circle skirt from the waist measurement and the skirt length.

- Page: https://www.acalculator.org/everyday-life/circle-skirt-calculator
- JSON spec: https://www.acalculator.org/everyday-life/circle-skirt-calculator.json
- Version: 7df6a9258423

## Default answer

Example with the default inputs (Skirt Full circle, Waist 28 in, Skirt length 22 in): Cut a waist radius of 4.456 in and an outer radius of 26.46 in; the pattern needs a 52.91 in by 52.91 in piece of fabric.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| style | Skirt | How much of a circle the skirt is: full, three quarters, half, or a quarter. |
| waist | Waist | The waist measurement where the skirt will sit, with any ease you want added. |
| length | Skirt length | The finished length from the waist seam to the hem. |
| hem | Hem and seam allowance (optional) | Extra length added below the finished length for the hem and the waist seam. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| radius | Waist radius | The radius of the waist cut-out: waist ÷ (2π × the fraction of a circle). |
| outer | Outer radius | The waist radius plus the skirt length plus the hem and seam allowance. |
| hemCircumference | Hem circumference | The length of the finished hem edge: 2π × (waist radius + skirt length) × the fraction of a circle. |
| fabricWidth | Fabric rectangle, width | The width of the smallest rectangle that holds the pattern in one piece. |
| fabricLength | Fabric rectangle, length | The length of the smallest rectangle that holds the pattern in one piece. |

## Method

waist radius r = waist ÷ (2π × f), f = 1, 3/4, 1/2 or 1/4; outer radius R = r + length + allowance; hem = 2π(r + length) × f; fabric rectangle = 2R × 2R (full, 3/4), 2R × R (half), R × R (quarter).

## Assumptions

- The waist measurement already includes any ease; the waist seam allowance is part of the optional allowance, added to the outer radius only.
- The pattern is cut in one piece; a skirt wider than the fabric is cut in more pieces, which needs seam allowance at each seam.
- Fabric stretch and bias drop at the hem are not included.

## Worked examples

1. style = full, waist = 0.7112, length = 0.5588 gives radius = 0.113191, outer = 0.671991, hemCircumference = 4.222244, fabricWidth = 1.343982, fabricLength = 1.343982. Source: Circumference of a circle C = 2πr (OpenStax Prealgebra 2e, section 9.5, https://openstax.org/books/prealgebra-2e/pages/9-5-solve-geometry-applications-circles-and-irregular-figures, retrieved 2026-10-01); NIST SP 811: 1 in = 0.0254 m.
2. style = half, waist = 0.7, length = 0.6, hem = 0.03 gives radius = 0.222817, hemCircumference = 2.584956, outer = 0.852817, fabricWidth = 1.705634, fabricLength = 0.852817. Source: Circumference of a circle C = 2πr (OpenStax Prealgebra 2e, section 9.5, https://openstax.org/books/prealgebra-2e/pages/9-5-solve-geometry-applications-circles-and-irregular-figures).
3. style = quarter, waist = 0.762, length = 0.508 gives radius = 0.485104, outer = 0.993104, hemCircumference = 1.559965. Source: Circumference of a circle C = 2πr (OpenStax Prealgebra 2e, section 9.5, https://openstax.org/books/prealgebra-2e/pages/9-5-solve-geometry-applications-circles-and-irregular-figures).

## FAQ

### How do I find the waist radius for a circle skirt?

Divide the waist by 2π for a full circle. For a 3/4 circle divide by 2π × 3/4, for a half circle by π, and for a quarter circle by π ÷ 2. A 28-inch waist gives a full-circle radius of 28 ÷ 6.2832 = 4.46 inches.

### How much fabric do I need for a full circle skirt?

A square of fabric 2 × the outer radius on each side, where the outer radius is the waist radius plus the skirt length plus any allowance. A 28-inch waist and 22-inch length need a square about 52.9 inches across, wider than most fabric, so many full circles are cut in two half-circle pieces.

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

The fraction of a circle the pattern covers. A full circle skirt has the most flare and the longest hem; a half circle has half the hem and less flare; a quarter circle is the slimmest and uses the least fabric.

### Do I add seam and hem allowance?

Add the hem allowance and the waist seam allowance in the allowance box; the calculator adds them to the outer radius so the fabric is big enough. Some sewists also take the waist seam allowance off the waist radius; the calculator does not.

### How do I mark the circles on the fabric?

Fold the fabric so the centre of the circle is at a corner, hold a tape measure there, and mark points at the waist radius and at the outer radius as you swing the tape. Join the points into two curves and cut along them.

### Why is my hem uneven after hanging the skirt?

Parts of a circle skirt fall on the bias, which stretches under its own weight. Hang the skirt for a day before hemming, then trim the hem level. The calculator does not include this drop.

## Sources

- OpenStax, Prealgebra 2e, section 9.5, Solve Geometry Applications: Circles and Irregular Figures (C = 2πr), CC BY 4.0, retrieved 2026-10-01. https://openstax.org/books/prealgebra-2e/pages/9-5-solve-geometry-applications-circles-and-irregular-figures
- NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B (1 in = 0.0254 m exactly). https://www.nist.gov/pml/special-publication-811