Circle Skirt Calculator (Waist Radius and Fabric)
Radius of the waist cut-out and the fabric you need for a full, half or quarter circle skirt from your waist measurement and the length you want.
Results
What this tool does
A circle skirt is cut as part of a ring, and its waist edge must be as long as your waist, so the waist radius is the waist divided by the angle in radians: waist ÷ 2π for a full circle, ÷ π for a half and ÷ (π/2) for a quarter. The hem radius is that plus the skirt length, which sets the fabric: a full circle needs a square twice the radius on each side, a half circle half of that depth, a quarter a square of one radius. Add some ease to the waist and a hem allowance, and let the skirt hang for a day before hemming, since the edge on the bias stretches.
Formula
waist radius = waist ÷ 2π (full circle), ÷ π (half), ÷ (π/2) (quarter) · hem radius = waist radius + skirt length
Variables
| Symbol | Meaning | Unit |
|---|---|---|
wa | Waist circumference | cm |
sl | Skirt length (waist to hem) | cm |
al | Hem allowance | cm |
ty | Kind of circle skirt | — |
RW | Radius of the waist cut-out | cm |
RH | Radius to the hem (without allowance) | cm |
FW | Fabric width needed (with allowance) | cm |
FD | Fabric length needed (with allowance) | cm |
Worked example
- Waist circumference70 cm
- Skirt length (waist to hem)55 cm
- Hem allowance2 cm
- Kind of circle skirt1
- Radius of the waist cut-out11.1 cm
- Radius to the hem (without allowance)66.1 cm
- Fabric width needed (with allowance)136 cm
- Fabric length needed (with allowance)136 cm
Limitations
- Always order a little more material than the calculated quantity. Cuts, breakage and pattern matching create waste that depends on the shape of the job.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.