Curtain Fabric Calculator
Enter your window, fullness, and fabric details to see how many drops to cut and how much fabric to order in yards or metres.
Fabric needed
How the estimate is built
The starting point is the gathered width: your track width multiplied by the fullness you want. Divided by the width of the fabric roll, that tells you how many vertical drops you need to sew together to make the pair. Each drop is then cut to the finished length plus allowances for the heading and hem, and rounded up to the pattern repeat so the design matches across seams.
Multiply the cut length by the number of drops and you have the total fabric, which the tool converts to yards or metres and rounds up to the nearest quarter — the way a fabric shop sells it. Treat the result as a confident minimum and buy a touch more for safety.
Frequently Asked Questions
What is curtain fullness?
Fullness is how much wider the flat fabric is than the window, so the finished curtain gathers into folds instead of hanging like a bedsheet. Around 2× the track width gives a classic pleated look; 1.5× gives a lighter gather; sheer voiles are sometimes 2.5–3× for a soft, full drape.
How does the pattern repeat affect how much I buy?
A patterned fabric repeats its design every so many inches or centimetres. So the motif lines up across every drop and between panels, each length is cut up to the next full repeat, which adds waste. The bigger the repeat, the more extra fabric you need — this calculator rounds each drop up to the repeat automatically.
What fabric roll width should I use?
Home-furnishing fabric is commonly 54 inches (137 cm) wide, which is the default here. Check the bolt — some fabrics are narrower or wider, and railroaded fabrics run differently. The roll width sets how many drops you can cut side by side to make up the total gathered width.
Should I add extra for hems and headings?
Yes — the calculator already adds a default allowance at the top for the heading and at the bottom for the hem, then you can raise it. Buy a little more than the minimum: it covers straightening the cut, matching a tricky repeat, and the odd measuring slip.
Estimates only. Fabric widths, repeats, and your chosen heading all change the total — check the bolt and your pattern before cutting, and keep the offcuts until the curtains are finished.