Curtain Panel Calculator
Enter your window and fabric details to find how much curtain fabric to buy and how wide each panel should be.
Planning curtain fabric
Good-looking curtains need more fabric width than the window itself — extra ‘fullness’ creates the soft folds curtains are known for when hung. Getting the fullness ratio and panel count right avoids buying too little (or too much) fabric.
The formula
Total flat fabric width needed is Window Width × Fullness Ratio, split evenly across your number of panels. This calculator then adds your hem and header allowance to the finished length to get a cut length per fabric drop, figures out how many fabric widths are needed per panel (rounding up), and multiplies out to a total yardage.
Patterned fabric may need extra yardage for pattern-matching between widths, which this calculator does not account for. Always round purchases up and check your fabric’s actual bolt width before buying. For general sewing planning purposes.