Pond Liner Calculator
Get the pond liner size right the first time. This pond liner calculator takes your pond length, width, max depth, and anchoring overlap and returns the exact liner width and length you need, plus the nearest standard off-the-shelf sheet size. Undersized liners fail fast; oversized liners waste hundreds of dollars. The standard formula accounts for the liner needing to drop down both sides and extend past the edge for anchoring under rocks or sod.
Pond Liner Size Formula
Calculate liner dimensions from pond dimensions using this rule:
- Liner width = Pond Width + (2 x Max Depth) + (2 x Overlap)
- Liner length = Pond Length + (2 x Max Depth) + (2 x Overlap)
The 2 x depth accounts for the liner dropping down both sides of the pond. The 2 x overlap (typically 2 feet per side) gives you enough material to anchor the liner under stones, sod, or edge coping.
Pond Liner Size Chart
Standard flexible liner sheets come in these common sizes:
| Liner Size (ft) | Max Pond L x W x D Covered |
|---|---|
| 10 x 10 | 4 x 4 x 1.5 ft |
| 10 x 15 | 9 x 4 x 1.5 ft |
| 15 x 15 | 7 x 7 x 2 ft |
| 15 x 20 | 12 x 7 x 2 ft |
| 20 x 25 | 16 x 11 x 2.5 ft |
| 20 x 30 | 21 x 11 x 2.5 ft |
| 25 x 30 | 20 x 15 x 2.5 ft |
| 30 x 40 | 30 x 20 x 2.5 ft |
| 40 x 50 | 40 x 30 x 2.5 ft |
Preformed vs Flexible Liners
Preformed pond shells (rigid plastic) are cheaper upfront and easier to install for small ponds under 300 gallons, but come in fixed shapes and sizes you can't customize. Flexible liners (EPDM rubber, RPE, PVC) cover any shape and any size, hold up better over 20+ years, and are the only option for custom or larger ponds. This calculator sizes flexible liners; for a preformed shell, match the shell's listed dimensions directly.
Where to Buy Pond Liners
Search "pond liner near me" on Google Maps to find local pond supply shops and landscape centers, which usually stock 10, 15, 20, 25, and 30 foot wide rolls. Big-box home improvement stores carry some small pre-cut sizes. Online retailers like Pondliner.com, Azponds, and Amazon ship custom-cut liner by the foot. EPDM runs $0.70-$1.20 per sq ft, RPE runs $0.40-$0.80 per sq ft, and PVC (cheapest, shortest life) is $0.30-$0.60 per sq ft.