Curtain Fabric Calculator
How many yards of fabric your curtains need
How to work out how much fabric you need for curtains
Curtains use far more fabric than a window is wide, because the fabric is gathered into folds to hang well. The trick to buying the right amount is to separate two questions: how wide the flat fabric must be (which depends on the window width and how full you want the curtains), and how long each cut piece must be (the finished drop plus the fabric turned under for the heading and hem). This curtain fabric calculator does both and gives you the yardage to buy.
Because fabric comes on a bolt of a fixed width, a wide curtain is made from several cut "drops" joined side by side. The calculator counts how many widths of your fabric are needed and multiplies by the cut length to reach the total.
Choosing a fullness ratio
- About 1.5× — a light, casual gather. Uses the least fabric.
- About 2.0× — a classic pencil-pleat look; the most common choice.
- About 2.2–2.5× — a deep, luxurious wave or pinch-pleat heading. Uses the most fabric.
Don't forget the extras
Two things routinely cause a fabric shortfall. The first is the heading and hem allowance: allow roughly 20 cm at the top and 20 at the bottom so there is enough to turn under. The second is a pattern repeat: with a printed or woven design you need extra length on every drop so the motif lines up where the widths are joined, otherwise the seam looks mismatched. When in doubt, buy a little extra — an off-cut is cheaper than a second trip for dye-lot-matched fabric.
Frequently asked questions
Should I measure the window or the curtain pole? Measure the pole or track, not the glass. Curtains should extend a little past the window on each side so they block light and look generous, and the pole is usually wider than the window for exactly that reason.
What is the fullness ratio? It is how many times the track width the flat, ungathered fabric measures. A 2× fullness on a track 122 cm wide means 244 cm of flat fabric gathered down to fit — that gathering is what gives curtains their folds.
Why round up to a whole cut? Fabric is cut from the bolt, so you buy whole lengths. Each drop is cut to the finished length plus its allowance, and you cannot use a partial drop, so the total is rounded up.
Does this include lining? No — it is the face fabric only. Lining is calculated the same way (usually at the same fullness), so if you are lining the curtains, buy a similar yardage of lining fabric.
These figures are planning estimates for standard gathered curtains. For blackout, interlined, or patterned makes, add a margin, and see our decorating guides for hanging tips.