Pond Liner Calculator
Enter your pond's length, width and depth to get the exact liner size you need, with enough overlap to anchor the edges.
A flexible pond liner has to drape down both sides, across the bottom, and up the other side — then overlap the edge so you can anchor it with stones or soil. This calculator adds twice the depth and twice your chosen overlap to each dimension.
How to work out pond liner size
To each of the length and width, add two times the depth (for the two sloping sides) plus two times the overlap (one flap on each edge).
Liner length = Pond length + (2 × depth) + (2 × overlap)
Liner width = Pond width + (2 × depth) + (2 × overlap)
Liner width = Pond width + (2 × depth) + (2 × overlap)
| Part | Why it's added |
|---|---|
| 2 × depth | Liner drops down and back up both sides |
| 2 × overlap | A flap on each edge to anchor the liner |
| Underlay | Buy the same size to protect the liner from stones |
Worked example
A 10 ft × 8 ft pond, 2 ft deep, with 2 ft of overlap:
| Liner length = 10 + (2×2) + (2×2) | 18 ft |
| Liner width = 8 + (2×2) + (2×2) | 16 ft |
| Liner size | 18 × 16 ft (288 sq ft) |
Frequently asked questions
How much overlap does a pond liner need?
Allow about 1–2 feet of liner past the edge on every side so you can fold it back and hold it down with rocks, paving or soil.
Do I need underlay too?
Yes — an underlay (or old carpet/sand) the same size as the liner protects it from sharp stones and roots, which greatly extends its life.
What if my pond has shelves or steps?
Use the deepest point for the depth. Steps and shelves use liner within that envelope, so measuring to the deepest part is a safe allowance.
Related calculators
Estimate for a simple rectangular pond. Irregular shapes, steep sides or large shelves may need extra liner — round up when buying.