A flounce is a circular ruffle cut from fabric donuts (rings). The inner circle attaches to the garment edge 1:1 — its circumference equals your attachment length — while the longer outer edge falls in soft waves. The flounce depth is the gap between inner and outer radius. Flounces create rippling movement without any gathering.

How does the flare ratio work?

Flare is the ratio of outer radius to inner radius (R ÷ r). The deeper the flounce relative to its inner radius, the curlier the ripple — so a smaller inner circle gives more flare. To make a flounce curlier than one donut allows, split the attachment edge across several smaller donuts: each has a smaller inner radius and therefore a higher flare ratio. A ratio around 2× gives soft waves; 3× or more is dramatically frilly.

What is the difference between a flounce and a ruffle?

A flounce is shaped (cut as a circle) so it naturally ripples without gathering. A ruffle is a straight strip that is gathered. Flounces hang more elegantly; ruffles have more uniform gathers.

How do I join multiple flounce circles?

Cut along one radius of each circle to open it into a spiral. Join the straight edges with seams (1.5 cm / ⅝" for garments). Press seams open. The combined inner edges of all the donuts should equal your attachment length so the flounce sits flat against the garment edge.

SewCalcs

Flounce Calculator — Circular Flounce Radii

Calculate inner and outer radii for circular flounces.

Attachment Length

Length of the garment edge the flounce stitches to (e.g. neckline, cuff, hem)

Flounce Depth

How far the flounce projects from the seam to its outer edge

Target Flare

Desired ripple: ~2× soft waves, 3× very frilly. Curlier flares split the edge into more, smaller donuts

Seam Allowance

Allowance on the inner edge that stitches to the garment (1.5 cm / ⅝″ typical)

Fabric Width

Usable fabric width (UK bolts ~90, 115 or 140–150 cm)

Fabric Price (optional)

Price per unit

How We Calculate This

A flounce is cut from circular rings (donuts) of fabric. The inner circle is stitched to the garment edge 1:1, so its circumference equals your attachment length; the longer outer circumference falls into ripples. The flounce depth is the gap between the two radii, and the flare comes from that gap relative to the inner radius — not from gathering.

The formula

Inner circumference = Attachment length (stitched 1:1)

Inner (seamline) radius r = Attachment length ÷ (2π)

Outer (cut) radius R = r + Flounce depth + Hem

Cut inner-hole radius = r − Seam allowance (allowance points inward)

Flare ratio = R ÷ r

Donuts to cut = enough to fit the fabric width and reach your target flare (split the attachment edge across smaller donuts for a curlier ripple).

Frequently Asked Questions

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Last updated: February 2026

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