What is the waist radius formula?

For a full circle skirt: Waist radius = Waist measurement / (2 x pi). For a half circle: Waist / pi. The radius determines where to draw the waist curve on the fabric. Always add seam allowance to the waist edge.

How do I cut a full circle skirt?

Fold fabric into quarters. Mark the waist radius from the folded corner, then mark the outer radius. Cut along both curves. If the outer radius exceeds the folded fabric size, cut two half-circles and seam them.

Why does a circle skirt hang unevenly at first?

The bias areas stretch under gravity. Hang the skirt for 24-48 hours, then level the hem by measuring up from the floor. This is especially important for longer circle skirts and lightweight fabrics.

What hem method works for circle skirts?

Use a narrow rolled hem (0.5-1cm) as wider hems will not lie flat on the curve. A serger rolled hem is ideal. Horsehair braid gives a beautiful structured hem. Avoid wide double-fold hems on full circles.

SewCalcs

Circle Skirt Calculator — Radius & Fabric

Calculate radius, fabric and cutting layout for circle skirts.

Waist Measurement

Including ease

Skirt Length

Finished length from waist to hem

Circle TypeFuller circle = more flare and more fabric

Hem Allowance

Narrow hem for circles

Fabric Width

UK bolts: 90/115/140-150cm; quilting cotton ~110cm

Fabric Price (optional)

Cost per metre for the cost estimate

How We Calculate This

The waist opening is a circle cut from the centre of a larger circle. The waist radius comes from the waist measurement and circle fraction.

The formula

Waist radius = Waist ÷ (2π × Circle fraction)

Outer radius (TR) = Waist radius + Skirt length + Hem + Waist seam allowance

Fabric depends on the outer diameter (2 × TR) versus the fabric width. If the diameter fits across the width, a full circle is cut whole on a quarter-fold and uses about 2 × TR of length. If the diameter is wider than the fabric, the skirt is cut as two half-circle panels rotated to run lengthways, so a full circle needs about 4 × TR of fabric plus the side-seam joins.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify quantities before cutting or purchasing fabric.