Fabric formula

Woven GSM from construction formula

Estimates woven fabric weight from ends and picks per inch, yarn counts and crimp, before a cut sample is available.

Formula
GSM≈39.37[EPI(1+C1)T1+PPI(1+C2)T2]1000\text{GSM} \approx \dfrac{39.37\left[\text{EPI}(1+C_1)T_1 + \text{PPI}(1+C_2)T_2\right]}{1000}

GSM ≈ 39.37 × [EPI × (1 + C1) × T1 + PPI × (1 + C2) × T2] / 1000

SymbolMeaningUnit
EPIEnds per inchthreads/in
PPIPicks per inchthreads/in
C₁Warp crimp as a fraction-
C₂Weft crimp as a fraction-
T₁Warp counttex
T₂Weft counttex

When to use it

Use it to sense-check a mill's construction sheet, plan a new quality, or estimate how a change in picks will move the weight.

Worked example#

Poplin 133 × 72, 40s × 40s cotton (14.76 tex each), warp crimp 8%, weft crimp 5%.

  • Warp = 133 × 39.37 × 1.08 × 14.76 / 1000 = 83.5 g/m²
  • Weft = 72 × 39.37 × 1.05 × 14.76 / 1000 = 43.9 g/m²
  • GSM ≈ 83.5 + 43.9 = 127.4 g/m²

39.37 converts threads per inch to threads per meter. Each thread in one square meter is one meter long plus its crimp, and tex divided by 1000 is grams per meter.

Where this formula is explained

Fabric & YarnGuide7 min read

Fabric GSM: Meaning, Formula, Measurement and Calculator

GSM is the weight of one square meter of fabric in grams. Learn how to measure it with a round cutter, calculate it from any sample size, estimate it from construction, and control it in production.

TestingHow-to3 min read

Fabric Construction Analysis: EPI, PPI, Count, Crimp and GSM

How to analyse a woven fabric sample: count ends and picks per inch, identify the weave, find warp and weft counts from yarn removed from the fabric, measure crimp and GSM, and write the construction in standard form.

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