Tarps can be classified based on a diversity of factors, such as material type (polyethylene, canvas, vinyl, etc, thickness, which is generally measured in millimeters or generalized into categories (such as "regular duty", "heavy duty", "super heavy duty", etc. and grommet strength (simple vs. reinforced), among others.
Tarps can also be classified by size-a common determining factor for consumers in acquiring tarps-and measured in width by length. Actual tarp sizes are generally about three to five percent smaller than the advertised size. (Thus, a tarp advertised as 20 ft. × 20 ft. will actually measure about 19 ft. × 19 ft. Some other factors that may influence a purchase decision include color (often they come in blue, green, black, or silver), grommet type (aluminum, stainless steel, etc.), and grommet-to-grommet distance (these often run between 18 inches and 5 feet). The weave count, a measure of tarp strength, often runs between (8 and 12 per square inch) and the greater the count, the greater its resistance against ripping in high wind conditions.Tarps may also be washable or non-washable and waterproof or non-waterproof, and mildewproof vs. non-mildewproof. Tarp flexibility refers to its ability to remain pliable during cold winter months; some tarps offer more flexibility than others in cold weather. Some manufacturers also advertise their tarps as "rot-proof", but this may be more an subjective than an objective measurement.
