There is no single metres-per-window rule. The amount you need depends on width, finished drop, heading, fabric width and any pattern repeat. Make a rough estimate first, then have the exact cutting plan checked before ordering an expensive fabric.
Start with the width
Measure the usable pole or track, including the area where curtains will stack. Multiply that width by the chosen fullness factor to estimate the total flat width. Divide by the usable fabric width after allowing for joining and side hems, then round up to a whole number of drops. For example, a 200 cm track at 2 times fullness needs around 400 cm of flat width. If usable fabric width were 135 cm, that suggests at least three widths before the maker adjusts for seams and heading construction.
Calculate each drop
Take the finished curtain drop and add allowances for the top and bottom hems and the heading method. Fabric shrinkage or preparation may also matter. Multiply the cutting length by the number of fabric widths to estimate total length. This is why a small change to the finished drop can affect the total order.
Allow for repeats and joins
For patterned material, each drop may need to start at the same point in the design. A vertical repeat can add substantial waste; a wide horizontal motif also needs thoughtful placement at seams and the centre opening. Fabrics sold as “wide width” may run horizontally and require a different plan. Ask how the pattern will be centred before purchasing.
Check the final order
Confirm the fabric’s actual width, batch availability, directional nap and laundering advice. Record the calculation, then ask the maker to approve the quantity for your particular heading and lining. Buying slightly too little can be difficult to fix if the same dye lot is unavailable later.
Practical checklist
- Measure the finished track width and drop
- Select heading and fullness
- Confirm the usable fabric width
- Add top and bottom allowances
- Calculate complete pattern repeats before ordering
Frequently asked questions
Can I calculate fabric from the window width alone?
No. Use the fitted pole or track width and include fullness, hems, seams, fabric width and pattern matching.
Why must fabric quantities be rounded up?
Curtains are cut from complete drops and patterned fabric often needs full repeats so adjacent panels align.
Should I buy extra fabric?
Ask the maker to approve the cutting plan. Extra from the same dye lot can be useful, but arbitrary over-ordering may create unnecessary waste.