This calculator works out how many metres of fabric you need to make curtains in New Zealand, taking the guesswork out of a job where buying too little means a mismatched dye lot and buying too much wastes expensive fabric. Curtains use far more material than the window size alone suggests, because they are gathered for a full look and each drop needs extra fabric turned under for the heading at the top and the hem at the bottom. The method is to take your track or window width and multiply it by a fullness ratio to find the total flat width the fabric must cover, then divide by the width of your chosen fabric to see how many widths, or panels, you need, and finally multiply those widths by the finished drop plus a hem and heading allowance. You enter the track width, the fullness ratio, the finished drop, the fabric width and the hem and heading allowance, and the calculator returns the number of fabric widths and the total metres to buy. A fullness of about two gives a comfortably gathered curtain, while sheers use more and a flat blind uses close to one. Patterned fabric needs extra to match the pattern across widths, so add a little more for that. An estimate to plan and budget your curtains.
Add extra for patterned fabric to match across widths. Rounds up to whole widths. An estimate for planning only.
The total flat width is the track width times the fullness ratio. The number of fabric widths is that flat width divided by the fabric width, rounded up to a whole number. Each width is cut to the drop plus the hem and heading allowance, and the total fabric is the number of widths times that cut length.
A 2 metre track at fullness 2 needs 4 metres of flat width. With 1.4 metre fabric that is 3 widths. Each is cut at 2.2 metres drop plus 0.25 metres allowance, so 2.45 metres, giving about 7.4 metres of fabric in total.
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