How the number is arrived at
A known area of finished sheet is cut and weighed, and the result is scaled to one square metre. Because it is a physical measurement of a sample, a real production run varies slightly around its nominal figure — which is why the manufacturing tolerance is a meaningful question to ask, and why a supplier who cannot state one is worth a second look.
The Double Kissan GSM tolerance is confirmed at enquiry.
What the number includes
- The woven HDPE tape fabric that forms the body of the sheet.
- The lamination applied to the fabric, which is what makes the surface shed water.
- Any additives present in the material as manufactured.
It does not include hems, eyelets or reinforcement tape, which is why the weight of a finished tarpaulin is always slightly more than its area multiplied by its GSM.
Three questions that matter more than the number
What is the tolerance?
A nominal 160 GSM sheet produced at the bottom of a wide tolerance band is a different product from one produced at the top of a narrow one — at the same advertised figure.
What is the lamination specification?
Waterproofing comes from the lamination. Two sheets at the same GSM with different lamination will behave differently in rain.
How are the edges and eyelets made?
Most tarpaulins fail at their edges. Edge reinforcement and eyelet fixing are separate specifications that GSM says nothing about.
A quick worked example
A sheet measuring 3 m × 4 m is 12 square metres. At 120 GSM that is roughly 1.44 kg of material; at 200 GSM, roughly 2.4 kg. That difference of just under a kilogram is what you gain in substance and what you lose in ease of handling. On a 6 m × 9 m sheet — 54 square metres — the same GSM step is a difference of over four kilograms, which is the point at which a one-person job becomes a two-person job.
The practical takeaway
GSM is a useful shorthand for comparing sheets of the same material and construction. It is not useful for comparing across materials, and it is not a substitute for asking about tolerance, lamination and edge construction.
Written by the Double Kissan team at Ashoka Poly Laminators Pvt. Ltd., Bareilly. Last reviewed November 2026.