How much fabric you need for curtains, hems and fullness included

How much fabric for curtains: the widths method

Multiply the rod width by the fullness, divide by the fabric width and round up: that gives the number of fabric widths. Then multiply the widths by the finished length plus the hem allowances to get the yardage. This is how curtain makers and fabric sellers such as Just Fabrics do it.

1. Rod. Window width plus the extension on each side. The Shade Store suggests about 6 to 12 in past the frame; Kirsch recommends at least 4 in. In the UK, Just Fabrics suggests 15-30 cm of pole on each side.
2. Fabric width needed. Rod × fullness, plus two side hems for every panel.
3. Widths. Fabric width needed ÷ fabric width, rounded up. With a pair, an odd number of widths is split down the middle: one and a half widths per panel.
4. Cut length. Finished length plus the header and hem allowances. If the fabric has a pattern, round up to a whole number of repeats so the pattern lines up across the widths.
5. Yardage. Widths × cut length, divided by 36 in.

Fullness depends on the heading. In the Just Fabrics guide eyelets (grommets) and pencil pleat take 2 times the pole width (up to 2.5 with deep tape), double pinch pleat 2.3, triple pinch pleat 2.5 and wave 2.3. The calculator starts from those figures: 2 for grommets and shirred tape, 2.5 for pinch pleats, 2.3 for ripplefold or wave. You can change them.

Railroaded fabric. Extra-wide fabric, such as the 118 in sheers sold by the linear yard at Canvas Etc, is turned sideways: the fabric width becomes the curtain length and you only buy the width, with no seams. It works as long as the finished length plus allowances fits in the fabric width.

Grommets and rings. Grommets are counted on the flat panel, about one every 6 1/4 in, and every panel needs an even number so both edges turn back toward the wall. Tape headings (shirred, pinch pleat, ripplefold) need a hook at each end and then one roughly every 4 in along the rod, with a ring for each hook.

A worked example

United States. A 36 in window, rod extending 6 in on each side, a pair of grommet panels 84 in long, fullness 2, 54 in fabric, plain, 14 in for header and hem, 2 in side hems. These are the values the calculator opens with in feet and inches.

• Rod: 36 + 2 × 6 = 48 in
• Fabric width needed: 48 × 2 = 96 in, plus 4 side hems of 2 in = 104 in
• Widths: 104 ÷ 54 = 1.93, so 2 widths, one per panel
• Cut length: 84 + 14 = 98 in
• Fabric: 2 × 98 = 196 in = 5.44 yd, so 5 1/2 yd rounded up to the quarter yard
• Grommets: each finished panel is 54 in less 4 in of side hems, 50 in wide, the same panel Sew4Home makes; 50 ÷ 6 1/4 = 8, an even number: 16 grommets

United Kingdom (metric). A 1.20 m window, 15 cm of pole either side, two eyelet curtains with a 2.50 m drop, fullness 2, 140 cm fabric, 25 cm of hems and 5 cm side hems. The pole is 1.50 m, the fabric width needed 3.20 m, so 3 widths (one and a half per curtain) of 2.75 m each: 8.25 m, 8.30 m cut to the next 10 cm, and 28 eyelets. With three whole widths the real fullness is 4.00 m over a 1.50 m pole, 2.67.

With pencil pleat tape instead of eyelets the fabric stays 8.30 m; you need 4.00 m of tape and 18 rings with hooks (9 per curtain). With a 64 cm pattern repeat each width goes up from 2.75 m to 3.20 m and the fabric to 9.60 m.

Curtain fabric chart by window width

A pair of grommet panels, rod 6 in past the window on each side, fullness 2, 54 in fabric, 14 in of header and hem, 2 in side hems. The figures come from the calculator.

Window	Rod	84 in long	96 in long
24 in	36 in	2 widths, 5 1/2 yd	6 1/4 yd
36 in	48 in	2 widths, 5 1/2 yd	6 1/4 yd
48 in	60 in	3 widths, 8 1/4 yd	9 1/4 yd
60 in	72 in	3 widths, 8 1/4 yd	9 1/4 yd
72 in	84 in	4 widths, 11 yd	12 1/4 yd

Windows of 24 and 36 in need the same two widths: on the smaller one the panels simply hang fuller. In metric, with 140 cm fabric and a 2.50 m drop, a 1.20 m window takes 3 widths and 8.30 m, a 2.00 m window 4 widths and 11.00 m.

Fabric widths, rods and grommets

Fabric width. Decorator fabric for curtains usually comes 54 in wide, the width Sew4Home uses; Just Fabrics gives 137 cm as typical in the UK. Use the width printed on the bolt or the product page. Extra-wide fabrics for railroading come around 118 in (300 cm in Europe).

Buying. The receipt rounds yards up to the quarter yard and metres up to the next 10 cm. Buy all the fabric at once from the same bolt so the color matches.

Rod. Measure the rod between the finials, not including them. Adjustable rods cover a range of lengths: pick one that reaches at least the length on the receipt.

Finished length. It runs from the top edge of the panel to the hem. With grommets the rod passes below the top edge, so measure from the top of the rod and add the heading above it; with rings and hooks measure from the point where the hook holds the panel. Kirsch hangs draperies about 1/2 in off the floor so they clear it when you open and close them.

Allowances. The calculator starts from 14 in for header and hem (Sew4Home: a 6 1/2 in folded header and a 7 1/2 in double hem) and 2 in per side hem, the minimum Sew4Home suggests. In metric it uses 25 cm, the Just Fabrics figure for pencil pleat, and 5 cm per side. For a deeper hem, raise them in the advanced options.

Grommets and hooks. The Sew4Home panel has 8 grommets 6 1/4 in apart, the calculator's starting spacing. For tape, Stitched puts a hook at each end and then roughly every 10 cm; Magic Linen gives 2 3/4 to 4 3/4 in (7 to 12 cm).

Common mistakes

• Starting from the window. Using the 1.20 m window instead of the 1.50 m pole gives 2 widths and 5.50 m: closed, the curtains barely cover the glass, and open they block part of it.
• Forgetting the allowances. Without the 25 cm per width the UK example would give 7.50 m instead of 8.25 m, and every width would come out short.
• Multiplying fractional widths. 2.29 widths × 2.75 m is 6.29 m, almost a whole width short. Lengthwise widths are bought whole (or in halves, shared between a pair).
• An odd number of grommets. One edge of the panel then turns toward the room.
• Railroaded fabric that is too narrow. A 2.90 m drop with 25 cm of hems is 3.15 m and does not fit in 300 cm fabric: you need widths sewn together.