High density polyethylene (HDPE) tarpaulin is a product with multiple end uses. HDPE fabric is laminated with LDPE, LLDPE or a blend of the two. It could be a three-layer tarpaulin having one layer of woven fabric and two layers of LDPE/LLDPE coating, one each on either side.

Waterproof HDPE Tarpaulin
It is 100% water proof and rot proof (optional), heavy in weight than all other tarpaulins, shrinks in length and width when it gets wet, biodegradable, Durable waterproof, non – breathiness

Speaking of durability, a good way to spot the best tarp is to check its thickness and the type of material used in the fabrication. The actual thickness of tarps is measured in mils (1/1000 of an inch). For general use, such as covering items, look for a lightweight blue tarp that has a thickness of at least 5 mm.

For knowing weight of Tarpaulin, one should know GSM, Length and Width of desired one.
By putting it in following formula, one can get approximate weight of Tarpaulin Weight=[{(L X B)/10.76} X (GSM/1000)]
weight in Kg, L and B in fee

Tarpaulins are graded and measured by GSM (Grams per Square Metre). This is basically a measure of the weight and thickness of the material from which the tarp is constructed. ... All our tarpaulins are waterproof, rot proof, UV protected with eyelets every metre and double edged, rope reinforced hems.

Generally speaking, the higher the mm rating, the more waterproof the fabric is. If some fabric is 2,000 gsm then it means that 2,000 grams of water can go through a square metre of the fabric over 24 hours.