Flexible pond-liner sizing tool
Pond Liner Calculator
Calculate the minimum flexible liner sheet, surface area, approximate pond volume, underlayment and cost for rectangular or round ponds.
Pond liner formulas
liner length = pond length + (2 × maximum depth) + (2 × edge overlap)
liner width = pond width + (2 × maximum depth) + (2 × edge overlap)
For a round pond, the calculator applies the same rule to the maximum diameter in both directions. Minimum sheet area is liner length × liner width. Purchase area adds the selected percentage, but it does not change either minimum sheet dimension.
The approximate water volume uses a rectangular prism or circular cylinder. Real ponds with shelves, sloped sides, rocks and freeboard usually hold less water, so use a measured fill volume when dosing treatments.
Checked example
| Input | Value |
|---|---|
| Pond | 12 ft long × 8 ft wide × 3 ft maximum depth |
| Overlap | 1 ft on every side |
| Allowance and price | 5% additional area; $0.85/ft² |
The minimum liner sheet is 20 × 16 ft, or 320 ft². A 5% purchase allowance gives 336 ft², with the minimum 20 × 16 ft dimensions still required. The rectangular-prism volume is about 2,154 US gal, and the estimated liner cost is $285.60.
Measurement limits and buying notes
- For irregular ponds, measure the longest length, widest width and deepest point rather than following the shoreline curve.
- Enter overlap per side. The formula adds it twice to each sheet dimension.
- Benches, shelves, vertical walls and deep narrow sections may need a larger sheet or a field measurement with a flexible tape.
- The additional area allowance is a purchasing estimate; a single sheet must still meet both calculated minimum dimensions.
- Do not use estimated geometric volume as the only basis for fish stocking, filtration design or chemical dosing.
Formula references: Pondliner.com sizing rule and World of Water measurement explanation.