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Weaving Calculations · Lecture 05
Weight of Fabric
From construction to ounces per square yard and grams per square metre — the calculation every merchandiser asks for first.
GSMoz/yd²Contractionlb/yd
Reading a construction
A woven construction is written warp count × weft count / ends per inch × picks per inch, width, weave: for example 20 × 20 / 60 × 60, 63", 1/1. Two corrections turn these numbers into yarn weight: warp contraction (the warp is longer than the fabric because it bends over the picks, about 10%) and weft contraction (the pick is longer than the fabric width, about 5%).
- Total ends = EPI × width. One yard of one end weighs 1 ÷ (840 × Ne) lb.
- Warp weight per yard of fabric = ends × (1 + warp contraction) ÷ (840 × Newarp).
- One pick is width (in yards) × (1 + weft contraction) long; there are PPI × 36 picks in a yard.
- Add the two, ×16 for ounces per linear yard, ÷ width in yards for oz/yd².
- Metric: lb/yd × 1.0936 = lb/m; ÷ 2.2046 = kg/m; ÷ width in metres × 1000 = GSM.
Fabric weight calculator
| A | B | C | |||
|---|---|---|---|---|---|
| 1 | Input | Fabric A | Fabric B | ||
| 2 | Warp count Ne | ||||
| 3 | Weft count Ne | ||||
| 4 | Ends per inch | ||||
| 5 | Picks per inch | ||||
| 6 | Width (inches) | ||||
| 7 | Warp contraction | ||||
| 8 | Weft contraction | ||||
| 9 | Warp | ||||
| 10 | Total ends | 3,780 | 8,064 | ||
| 11 | Weight of 1 yd of one end (lb) | 0.000060 | 0.000060 | ||
| 12 | Warp weight per yd of fabric (lb) | 0.2475 | 0.5280 | ||
| 13 | Weft | ||||
| 14 | Length of one pick (yd) | 1.8375 | 1.8375 | ||
| 15 | Picks per yard | 2,160 | 2,160 | ||
| 16 | Weft weight per yd of fabric (lb) | 0.2363 | 0.2953 | ||
| 17 | Results | ||||
| 18 | Yarn per linear yard (lb) | 0.4838 | 0.8233 | ||
| 19 | Ounces per linear yard | 7.74 | 13.17 | ||
| 20 | Ounces per square yard | 4.42 | 7.53 | ||
| 21 | Yarn per linear metre (kg) | 0.2400 | 0.4084 | ||
| 22 | GSM (g / m²) | 149.96 | 255.22 | ||
blue = input (edit me)grey = formula (click to see it)
Fabric A (20×20/60×60) comes out at 4.42 oz/yd² ≈ 150 GSM, a typical sheeting; fabric B (20×16/128×60, 3/1 twill) at 7.53 oz/yd² ≈ 255 GSM, a drill. A quick check: oz/yd² × 33.9 = GSM.
Rough estimate used on the shop floor
Fabric Design Lecture 2 gives a quick rule for Ne-count cotton fabrics: GSM ≈ ( EPI ÷ Newarp + PPI ÷ Neweft ) × 25. For fabric A that is (3 + 3) × 25 = 150; for B (6.4 + 3.75) × 25 = 254. It ignores contraction and width, which is why the exact method above is preferred for quotations.
Original lecture material
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