Curtain fabric calculator: widths, drop and pattern repeat
This curtain fabric calculator turns your track width and drop into the number of fabric widths and the metres to buy. It allows for fullness, heading and hem, side hems, the fabric lost at each join and the vertical pattern repeat, and works in centimetres or inches.
The method is the one used by the curtain fabric calculators of fabric houses and curtain makers: multiply the track by the fullness, divide by the cloth width and round up to whole widths; then add the heading and hem to the drop, round up to the repeat, and multiply. Everything runs in your browser.
How to use the Curtain Fabric Calculator
- Measure the track or pole width (the length the curtains will cover) and the drop from the track to the finished hem.
- Choose a heading style or type your own fullness, and tick pair if you are making two curtains.
- Adjust the heading, hem, side hem and join allowances if your maker uses different ones.
- Enter the fabric width and the pattern repeat (0 for a plain cloth).
- Read the widths and the metres to buy, and copy the working for the shop.
Curtain Fabric Calculator features
Whole-width rounding
Widths are rounded up, and to an even number for a pair so both curtains match.
Pattern repeat
The cut length is rounded up to a whole repeat so patterns line up across joins.
Visible working
The table shows each step so you can compare with a supplier’s figure.
Editable allowances
Side hems, joins, heading and bottom hem are inputs, not hidden constants.
The formula
Fabric suppliers describe the same steps: William Morris & Co, Jane Clayton and Direct Fabrics (read 19 October 2026) multiply the track by the fullness, divide by the cut width (commonly 137 cm) and round up; one adds about 30 cm per drop for hems and heading, and the others round the drop up to the repeat (a 185 cm drop on a 25 cm repeat becomes 8 repeats, 200 cm). They do not agree on a side hem allowance, so it is an input here. Tracks usually extend 15 to 35 cm beyond each side of the window, so measure the track itself rather than the window.
- Fabric needed across = track width × fullness + side hems (per curtain).
- Widths = that figure ÷ (fabric width − join allowance), rounded up; for a pair, rounded up to an even number.
- Cut length = drop + heading allowance + bottom hem, rounded up to a whole pattern repeat.
- Total = widths × cut length, rounded up to the next 0.1 m.
Choosing fullness
Fullness is how many times wider the fabric is than the track. Suppliers quote 1.5 to 2.5 times, with 2 to 2.5 the usual choice for gathered headings and about 1.5 to 2 for eyelets and tabs; the figures in the heading list are typical values, so follow your heading tape or maker if they state a different one. Sheer fabrics usually look better with more fullness, and heavy fabrics may need less.
| Example | Value |
|---|---|
| Track 240 cm × 2 + 16 cm side hems | 496 cm across |
| Usable width 137 − 3 cm | 134 cm each |
| Widths 496 ÷ 134 = 3.7 | 4 widths (2 per curtain) |
| Cut length 220 + 12 + 18 | 250 cm |
| Total 4 × 250 cm | 10 m |
Limits
This is an estimate for plain flat curtains. Linings, interlinings, weights, half-drop repeats, railroaded fabrics (turned on their side) and very wide cloth need their own allowances. If you are sewing from measurements of clothes see the fabric calculator for clothing; for wall coverings use the wallpaper calculator.
Curtain Fabric Calculator FAQ
How much fabric do I need for curtains?
Multiply the track width by the fullness, divide by the usable fabric width and round up to get the number of widths, then multiply by the drop plus about 30 cm for heading and hem.
What fullness should I use?
Between 1.5 and 2.5 times the track width. Gathered headings usually use 2 to 2.5; eyelets and tabs often less. Follow the heading tape or your curtain maker.
How do I allow for a pattern repeat?
Add the heading and hem to the drop, then round up to the next whole repeat. This keeps the pattern aligned across every width.
How wide is curtain fabric?
Furnishing fabric is commonly 137 or 140 cm (54 in) wide; some are 280 cm for seamless wide curtains. Check the bolt.
Why does a pair need an even number of widths?
So both curtains have the same number of widths and hang evenly. The calculator rounds up to the next even number for a pair.
Does this include lining?
No. Order lining separately, usually with the same drop and slightly narrower widths.