Flounce Calculator — Circular Flounce Radii

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.

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.

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.

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.