Curtain Calculator
How much curtain fabric to buy: the widths (drops) for the track or pole at the fullness you choose, the cut drop with hems, heading and pattern repeat, and the total length, in centimetres or inches.
Result…
How it's calculated
Flat width = (track width + returns and overlap) × fullness Widths = flat width ÷ fabric width, rounded up Cut drop = finished drop + hem + heading, rounded up to whole pattern repeats Fabric = widths × cut drop (÷ 100 for metres, ÷ 36 for yards)
Curtains are made from whole widths of fabric sewn side by side. The flat fabric must be wider than the track so it gathers into folds: that multiple is the fullness, and the heading style decides how much it needs. Divide the flat width by the roll width and round up to get the widths (also called drops). Each one is cut to the finished drop plus the hem and heading, and patterned fabric is rounded up to whole repeats so the pattern lines up across the widths. Multiply to get the fabric to buy. Every allowance here is yours to set from the pattern or maker.
Your numbers, step by step
About the Curtain calculator
This curtain calculator works out how much fabric to buy for a pair of curtains or a single curtain. It starts from the track or pole width, multiplies by the fullness you choose so the fabric gathers into folds, and divides by the width of the roll to find how many widths (also called drops) to sew together. Each width is cut to the finished drop plus the bottom hem and the heading allowance, rounded up to whole pattern repeats for patterned fabric so the design lines up across the seams. The total comes out in metres or yards, with every step shown. It works in centimetres or inches, and every allowance is yours to set from the pattern, the heading tape or the curtain maker, so it suits home sewers and anyone checking a quote before ordering fabric.
How to use it
- Pick the “Units” and enter the “Track or pole width”, plus any “Extra for returns and overlap”.
- Choose the “Fullness” the heading needs, and whether the “Curtains” are a pair or one curtain.
- Enter the “Fabric width” from the roll's label and the “Finished drop”.
- Set the “Bottom hem allowance”, the “Heading allowance” and the “Pattern repeat” (0 for plain fabric).
- Read the fabric to buy, the number of widths and the cut drop.
Worked example
A pair of curtains on a 180 cm track at 2 × fullness, in 140 cm wide fabric with a 32 cm pattern repeat. Flat width = 180 × 2 = 360 cm, and 360 ÷ 140 = 2.57, so 3 widths: 1.5 per curtain, with one width cut in half lengthways. Cut drop = 220 cm finished + 15 cm hem + 10 cm heading = 245 cm, and 245 ÷ 32 = 7.66 repeats, rounded up to 8 repeats = 256 cm. Fabric = 3 × 256 cm = 768 cm, so buy 7.68 m (about 302 inches). The fullness you actually get is 3 × 140 ÷ 180 = 2.33 ×.
Updated
Questions people ask
How do I calculate how much fabric I need for curtains?
Multiply the track width by the fullness and divide by the fabric width, rounding up to whole widths. Multiply the widths by the cut drop (finished drop plus hem and heading, rounded up to the pattern repeat) to get the length to buy.
What does curtain fullness mean?
It is how many times wider the flat fabric is than the track. At 2 × fullness a 180 cm track needs 360 cm of flat fabric; a higher ratio gives deeper folds and uses more fabric.
Why does a pattern repeat add fabric?
Each width must start at the same point in the pattern so the design lines up across the seams. That means each cut drop is rounded up to whole repeats, and the extra is wasted at the end of each cut.
What is a common mistake when measuring for curtains?
Measuring the window instead of the track or pole. The curtains hang from the track, which is usually wider than the window, so measure the track and the drop from it.
Does this include lining and side hems?
No. Work out the lining the same way with its own width, and check the pattern for side hems and any extra repeat for matching the first cut. For other room projects, the wallpaper calculator works with rolls and pattern repeats too.