A liner must cover the sides and anchoring edges
A rectangular liner must cross the bottom, travel up both sides and leave material at both edges for the stated overlap. This uses the intended maximum depth, unlike a water-volume estimate that uses average depth. The simple formula does not trace irregular shelves or contours.
Measure and calculate
- Measure the pond’s planned length and width.
- Enter maximum depth and the anchoring overlap needed at each edge.
- Check length, width and area modes before choosing a liner size that the supplier offers.
Liner length = pond length + 2 × depth + 2 × overlap; liner width follows the same rule.
A worked example
- Inputs
- A 10 by 6 ft pond has a 2 ft maximum depth and 1 ft overlap at every edge.
- Calculation
Length: 10 + 4 + 2 = 16 ft. Width: 6 + 4 + 2 = 12 ft. Liner area: 16 × 12 = 192 ft².- Result
- 16 ft liner length
The initial result is a 16 ft liner length. The corresponding width is 12 ft. Confirm contour and anchoring requirements before treating the rectangular estimate as a final cut size.
Read the result
| Output or check | What it means for your project |
|---|---|
| Liner length and width: ft | Each dimension includes the bottom span, two side depths and overlap at both edges. Use maximum depth for this sizing method. |
| Liner area: ft² | Area is the product of the two calculated liner dimensions. Check the supplied sheet dimensions, contours and anchoring detail before selecting a stock size. |
Common questions
Why add depth twice?
The liner crosses two opposing sidewalls, so both sides need to be included in each overall dimension.
Is liner depth the same as average water depth?
No. Liner sizing uses the depth needed to cover the excavation. Water-volume calculations use an appropriate average filled depth.