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.
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.