Gathering Ratio Calculator

The strip you gather always starts longer than what it gathers down to — how much longer depends on the fullness you want.

The length of the seam or edge the gathered strip will attach to once it's sewn in.
How full and voluminous you want the gathered result to look — higher ratios use more fabric per finished inch.

What the ratio means

A 2:1 ratio means the strip you cut is twice as long as the seam it gets gathered into — every inch of finished, gathered edge is made from two inches of flat fabric. Higher ratios pack in more fabric per inch, giving a fuller, more voluminous gather.

Choosing a ratio

1.5:1 gives a subtle, controlled gather that reads more like soft pleating. 2:1 is the standard, reliable choice for most ruffles and gathered skirts. 3:1 and above start to look genuinely full and voluminous, but also use significantly more fabric and take longer to gather evenly.

Fabric weight changes how a ratio looks

The same 2:1 ratio looks noticeably fuller in a lightweight, drapey fabric than in something stiff or heavy, since heavier fabric resists compressing into small folds. Go up a ratio tier for stiffer fabrics if you want the same visual fullness you'd get from a lighter one.