Fabric Calculator
Work out how much fabric to buy for curtains, allowing for fullness, hems and pattern repeat.
About the Fabric Calculator
Enter the rail width, finished drop, fullness, fabric width, hem and heading allowances and pattern repeat. The calculator gives the number of fabric widths, the cut length of each and the total fabric to buy.
Curtains need more fabric than the window width to hang in folds: multiply the rail width by the fullness ratio and divide by the fabric width to get the number of widths (drops). Each drop is the finished length plus hem and heading allowances, rounded up to whole pattern repeats so patterns match.
The formula
Fabric = ⌈rail × fullness ÷ fabric width⌉ × (drop + allowances)
Worked example
An 80 in rail, 87 in drop, 2× fullness, 54 in fabric, 12 in allowances
- 80 × 2 ÷ 54 = 2.96, so 3 widths
- Each cut 87 + 12 = 99 in
- 3 × 99 in = 297 in = 8.25 yards
Questions people ask
How much fullness?
2× is a good default; sheers often use 2.5–3×.
Do I need lining?
Same quantity of lining, without pattern matching.