Pond Liner Calculator (Liner Size and Volume of a Garden Pond)
The size of liner to buy for a garden pond from its length, width and depth, with the underlay area, the surface and a volume estimate.
Results
What this tool does
A liner must cover the bottom, climb both sides and still lap over the bank, so each dimension is the pond's length (or width) plus twice the maximum depth plus twice the overlap — the standard rule, which uses the deepest point because the liner is laid in folds over the shelves and corners. About 30 cm of overlap each side is common. The underlay needs the same size. For volume, a pond is never a full box: sloping sides and shelves make it hold roughly 0.7 of length × width × depth, and a kidney or free-form shape is nearer that than a straight-sided one. Treat the litres as a guide when dosing treatments or sizing a pump.
Formula
liner = (length + 2 × depth + 2 × overlap) × (width + 2 × depth + 2 × overlap) · volume ≈ length × width × depth × shape factor
Variables
| Symbol | Meaning | Unit |
|---|---|---|
pl | Length of the pond | m |
pw | Width of the pond | m |
pd | Deepest point | m |
po | Overlap on the bank, each side | m |
vf | How much of the box shape the pond fills | — |
AR | Liner area | m² |
LL | Liner length | m |
LW | Liner width | m |
VL | Volume of water | L |
SF | Water surface | m² |
Worked example
- Length of the pond4 m
- Width of the pond3 m
- Deepest point0.8 m
- Overlap on the bank, each side0.3 m
- How much of the box shape the pond fills0.7
- Liner area32.2 m²
- Liner length6.20 m
- Liner width5.20 m
- Volume of water6720 L
- Water surface12.0 m²
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- Always order a little more material than the calculated quantity. Cuts, breakage and pattern matching create waste that depends on the shape of the job.