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Quick answer
GSM means grams per square metre — the weight of one square metre of the sheet. Within the same material, a higher GSM usually means a thicker, stronger tarpaulin. As a rule of thumb: 90–150 GSM for light, short-term cover; 160–250 GSM for regular outdoor use; 450–650 GSM PVC for trucks and heavy daily use. To check a sheet, weigh it and divide the grams by its area in square metres.
Key takeaways
- GSM = grams per square metre. It measures weight, not thickness.
- Compare GSM only within one material — 200 GSM PE and 200 GSM canvas behave very differently.
- Sheet weight (kg) = GSM × area (m²) ÷ 1000.
- 1 sq ft = 0.0929 m², so a 12 × 18 ft sheet is about 20 m².
- Weigh a sheet to confirm its GSM; hems, rope and eyelets add a little.
What GSM means
GSM stands for grams per square metre. Cut a piece of tarpaulin exactly 1 m × 1 m and weigh it: if it weighs 200 grams, the sheet is 200 GSM. Heavier sheets carry more fabric and more coating, so GSM is the quickest way to compare grades of the same material.
GSM is a weight, not a thickness. PVC is denser than polyethylene, so it packs more grams into the same thickness — a 200 GSM PE sheet and a 200 GSM PVC sheet are not the same thing. Always compare GSM within one material.
Which GSM do you need?
| GSM range | Material | Duty | Typical uses |
|---|---|---|---|
| 60–90 | PE | Very light | Dust sheets while painting, one-off covering |
| 100–150 | PE | Light | Short-term outdoor cover for weeks to a few months, light packing |
| 160–200 | PE or parachute | Medium | Building sites, godown stock, a season on a rooftop |
| 200–250 | Heavy PE | Heavy | Monsoon roof cover, long-term storage, occasional truck use |
| 450–550 | PVC | Heavy | Stack covers, curtains, awnings, cricket pitch covers |
| 550–650+ | PVC | Extra heavy | Daily truck covers, tensile structures, tank liners |
Heavier isn't always better: a heavy sheet is harder to lift, tie and fold. Pick the lightest grade that will survive the job.
Work out a sheet's weight
Sheet weight
weight (kg) = GSM × area (m²) ÷ 1000
Example: A 200 GSM sheet of 12 × 18 ft is 216 sq ft ≈ 20.07 m², so it weighs about 200 × 20.07 ÷ 1000 ≈ 4.0 kg.
Sizes in Pakistan are usually quoted in feet. To convert, multiply square feet by 0.0929 to get square metres. The table below gives approximate weights for common sizes.
| Size | Area | 120 GSM | 200 GSM | 250 GSM | 650 GSM |
|---|---|---|---|---|---|
| 6 × 9 ft | 54 sq ft ≈ 5.0 m² | 0.6 kg | 1.0 kg | 1.3 kg | 3.3 kg |
| 9 × 12 ft | 108 sq ft ≈ 10.0 m² | 1.2 kg | 2.0 kg | 2.5 kg | 6.5 kg |
| 12 × 18 ft | 216 sq ft ≈ 20.1 m² | 2.4 kg | 4.0 kg | 5.0 kg | 13.0 kg |
| 18 × 24 ft | 432 sq ft ≈ 40.1 m² | 4.8 kg | 8.0 kg | 10.0 kg | 26.1 kg |
| 24 × 30 ft | 720 sq ft ≈ 66.9 m² | 8.0 kg | 13.4 kg | 16.7 kg | 43.5 kg |
Weights are for the fabric only. Hems, rope and eyelets add a little.
How to check the real GSM of a sheet
Measure the sheet
Measure the finished width and length in feet, edge to edge.
Work out the area
Multiply width × length, then × 0.0929 for square metres. A 9 × 12 ft sheet is 108 sq ft ≈ 10.03 m².
Weigh it
Use a hanging or platform scale. Say the sheet weighs 2.1 kg (2,100 g).
Divide
GSM = grams ÷ square metres. 2,100 ÷ 10.03 ≈ 209 GSM.
GSM, microns and mils
Plastic film — greenhouse sheet and polythene rolls — is sold by thickness in microns (µm), not GSM. One micron is a thousandth of a millimetre, so 200 micron = 0.2 mm. Imported sheets sometimes quote mils: 1 mil = 25.4 microns.
For solid polyethylene film you can convert roughly: GSM ≈ microns × 0.92, because polyethylene weighs about 0.92 g per cm³. This does not work for woven tarpaulins, which have gaps in the weave and coatings of a different density.
| Thickness | Millimetres | Mils | Approx. GSM |
|---|---|---|---|
| 25 micron | 0.025 mm | 1.0 mil | ≈ 23 GSM |
| 50 micron | 0.05 mm | 2.0 mil | ≈ 46 GSM |
| 100 micron | 0.1 mm | 3.9 mil | ≈ 92 GSM |
| 150 micron | 0.15 mm | 5.9 mil | ≈ 138 GSM |
| 200 micron | 0.2 mm | 7.9 mil | ≈ 184 GSM |
| 250 micron | 0.25 mm | 9.8 mil | ≈ 230 GSM |
Choosing greenhouse or tunnel film? See the greenhouse film guide.
What GSM doesn't tell you
- Weave: in PE tarpal, a tighter weave — more strips per inch — resists tearing better at the same GSM.
- Coating quality: thin or patchy lamination can leak, even on a heavy sheet.
- UV treatment: in full sun, a UV-stabilised 180 GSM sheet can outlast an untreated 250 GSM one.
- Finishing: double-stitched hems, rope-reinforced edges and rust-proof eyelets matter as much as the fabric.
Written by the team at Marfani Enterprises, Jodia Bazaar, Karachi. Figures are typical ranges for guidance — ask us about your exact job. Updated 27 September 2026.
