Curtain fabric calculator

Curtains

A pair for a 2 m track, 2.2 m long, at 2 × fullness in 137 cm fabric with 25 cm for hems: 4 widths each cut to 2.45 m, 9.8 m in all. With a 64 cm pattern repeat each cut grows to 2.56 m and you need 10.88 m.

Widths = ⌈(track × fullness ÷ curtains + side hems) ÷ fabric width⌉ per curtain
Fabric = widths × (length + hems, rounded up to whole repeats) + one repeat

Fullness by heading

Fullness is how much wider the fabric is than the track, so the curtains hang in folds when closed. These are the usual ranges; the tape or heading maker’s instructions say what theirs needs.

Pieces from a roll

For cushion covers and the like, the calculator lays pieces in rows across the fabric, turned whichever way uses less: six 50 × 50 cm pieces from 137 cm fabric fit 2 to a row, 3 rows, 1.5 m of fabric.

How to read the result

• Fabric to buy: rounded up to the next 10 cm (or ⅛ yard).
• Widths: how many fabric widths are joined for each curtain.
• Each cut length: the drop plus hems, matched to the pattern.

Common mistakes

• Measuring the window instead of the track or pole.
• Choosing too little fullness for the heading.
• Forgetting the extra repeat to line up a pattern.

How to use it

1. Choose Curtains or Pieces.
2. For curtains, type the track width, the finished length, a pair or one, the fullness and the fabric width and repeat.
3. Read how much to buy, rounded up to the next 10 cm (or eighth of a yard).

Questions

How much fabric for a pair of curtains?

For a 2 m track and 2.2 m drop at 2 × fullness in 137 cm plain fabric, about 9.8 m.

What does fullness mean?

How many times the track width the fabric is, so the curtains gather in folds. Pencil pleat usually needs 2 to 2.5 times.

Should I allow for shrinkage?

Yes, for washable fabrics: pre-wash them or add a few per cent. Cotton can shrink 3–5%.

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