Use these formulas to calculate how much material you'll need (all dimensions in feet):
Liner length=pond length+(2 x depth)+2.
Liner width=pond width+(2 x depth) +2.
Multiply liner length by liner width to get total square footage.Synthetic rubber
The best choice for most ponds, 45-mil-thick EPDM comes in sheets up to 50 by 200 feet. Durable, UV resistant, and flexible to -40 degrees F. Not to be confused with roofing EPDM, which has additives that kill fish.
About 67 cents per sq. ft.; GrayStone CreationsPlastic
Liners made of polyethylene (PE) and reinforced polypropylene (RPP) are thinner, lighter, and less expensive than EPDM but stiffer and harder to work with. Sizes up to 40,000 sq. ft. Like EPDM, they carry a 20-year warranty. Avoid PVC liners; they have a short life span when exposed to sunlight.
20-mil PE, about 30 cents per sq. ft., and 36-mil RPP, about 45 cents per sq. ft.; Pond Liner