How to calculate curtain fabric requirements
Use usable fabric width and finished drop. Widths are rounded per panel and lengths can be rounded to a vertical repeat. Check your sewing plan before cutting.
- Measure the rail and choose the drop.
- Choose fullness, panels and usable width.
- Add hems, top allowance and pattern repeat.
Formula
Width per panel = rail × fullness ÷ panels. Fabric widths per panel = panel width ÷ usable fabric width, rounded up. Cut length = drop + hem + top allowance, rounded up to the pattern repeat when present.
Two panels for a 2 m rail
Fullness 2 and usable fabric width 1.4 m require 2 fabric widths per panel, 4 in total. A 2.4 m drop + 0.2 m hem + 0.1 m top gives 2.7 m. A 0.32 m repeat rounds this to 2.88 m per width: 11.52 m total.
- Panels are equal and use vertical fabric widths.
- Entered fabric width already excludes selvedges and required seam losses.
- Lining, shrinkage, alternating patterns and horizontal repeats are not added.
Frequently asked questions
What does fullness 2 mean?
The planned flat fabric width is twice the rail width. Check the factor required by your heading and chosen fabric.
Why round each panel separately?
Each panel needs enough whole fabric widths for its own width. Rounding only the combined total can leave a panel short.
Will the pattern definitely match?
No. The calculation rounds cut length to the vertical repeat. Starting position and alternating designs may need extra planning.