Fabric & consumption calculator

Fabric GSM Calculator

Calculate fabric GSM from a round cutter or any rectangular sample, or estimate it from woven construction (EPI, PPI, counts, crimp) or single jersey loop geometry.

Result

Fabric GSM

180g/m²

Weight in oz/yd²: 5.31oz/yd²
Sample area: 100cm²
Equivalent 100 cm² cutter weight: 1.8g

Compare against the ordered GSM and the tolerance agreed with the buyer. Many buyers work to a plus or minus 5% tolerance, but always use the figure in your specification.

Working

Sample weight = 1.8 g
Sample area = 100 cm² = 0.01 m²
GSM = 1.8 / 0.01 = 180 g/m²

Formulas

Measured GSM

\text{GSM} = \dfrac{W}{A} \times 10\,000

Symbol	Meaning	Unit
W	Sample weight	g
A	Sample area	cm²

Woven estimate

\text{GSM} \approx \dfrac{39.37\,[\text{EPI}(1+C_1)\,T_1 + \text{PPI}(1+C_2)\,T_2]}{1000}

Symbol	Meaning	Unit
EPI, PPI	Ends and picks per inch	threads/in
C₁, C₂	Warp and weft crimp as a fraction	-
T₁, T₂	Warp and weft linear density	tex (g/km)

Knit estimate (single jersey)

\text{GSM} \approx \dfrac{\text{CPI} \times \text{WPI} \times 1550 \times \ell \times T}{10^{6}}

Symbol	Meaning	Unit
CPI, WPI	Courses and wales per inch	per in
ℓ	Stitch length	mm
T	Yarn linear density	tex
1550	Square inches per square meter (39.37²)	in²/m²

How the calculator works#

Choose one of four methods:

Round cutter: enter the sample weight and the cutter area. Most cutters cut 100 cm², so GSM is simply the weight multiplied by 100.
Rectangle: enter the weight and the length and width of any rectangular sample, in centimeters or inches.
Woven estimate: enter ends and picks per inch, warp and weft counts in Ne, tex, Nm or denier, and the crimp of each. The calculator converts each count to tex and adds the warp and weft weights.
Knit estimate: enter courses and wales per inch on relaxed fabric, the stitch length and the yarn count.

Every result also shows the weight in oz/yd² and the full working, so you can check the arithmetic or paste it into a report.

Worked example#

A quality checker cuts five samples with a 100 cm² cutter from a finished 180 GSM order. The average weight is 1.84 g.

GSM = 1.84 × 100 = 184 g/m², which is 2.2% above the 180 target and inside a plus or minus 5% tolerance.

Interpreting the result#

Compare the result with the target and tolerance in your fabric specification, and record the fabric state (grey, finished or after wash). If a construction estimate and a measured GSM disagree by more than a few percent, check yarn count, stitch length or picks, and the finishing width. A fabric pulled wide on the stenter reads light and often shrinks later.

Assumptions

The measured method is the reference. Construction methods are estimates for planning and cross-checking.
Samples should be conditioned in a standard atmosphere before weighing, because moisture changes weight.
The woven estimate ignores size, finish add-on and weight changes from dyeing and finishing.
The knit estimate assumes one loop per course per wale (single jersey type). Rib, interlock and fleece need the measured method.

Common errors

Cutting samples near the selvedge or from a creased area, which gives an unrepresentative weight.
Using a blunt cutter that frays the edge and loses fibre from the sample.
Weighing a single sample. Take at least three to five across the width and average them.
Mixing Ne and tex, or entering picks per cm as PPI.

Questions

How many samples should I weigh for GSM?

At least three, taken across the width and away from the selvedge, and preferably five. Report the average and the range; a large range tells you the fabric is uneven.

Why does my lab GSM differ from the construction estimate?

Construction estimates do not include finishing effects such as compaction, stretching on the stenter, brushing, chemical add-on or moisture. Use the estimate for planning and the cut sample for acceptance.

Can I use the knit estimate for rib or interlock?

No. The knit method assumes one loop per course per wale, which fits single jersey structures. Double-knit fabrics have loops on two needle beds, so weigh a cut sample instead.

Related formulas

Guides for this calculation

Fabric & YarnGuide7 min read