How to size a pond liner
- For a planned pond, enter its maximum length, width and vertical depth at the rim. The estimate adds twice the depth and twice the per-side edge allowance to each dimension.
- For an excavated pond, run a flexible tape from rim to rim along the actual basin floor and ledges. Enter the two contour measurements; only the edge allowance is added.
- Compare both required dimensions with sheets you can buy. A larger area alone does not mean a sheet will fit.
Why the two measurement methods differ
A tape laid over the finished basin has already travelled down and up the sides. Adding the depth again would count that travel twice. The formula based on rim dimensions is a conservative estimate for a simple basin; unusual slopes, overhangs or shelves should be checked with a physical tape measurement.
Source and limits
The per-side formula follows Omni's pond sizing guide. The contour method follows BTL Liners' measurement guide. Supplier allowances vary: this tool lets you set yours explicitly. It does not design seams, estimate fish capacity, or size a connected stream or waterfall.
Pond liner FAQ
How much edge allowance should I enter?
Enter the allowance you need on each side, not the combined allowance for both sides. Check your liner supplier's installation guidance for the edging and anchoring method you will use.
Do I add the pond depth after measuring the excavated basin with a tape?
No. If the flexible tape followed the basin from rim to rim over the bottom and shelves, that measurement already includes the depth path. Add only the edge allowance on each side.
Will a liner fit if its area is larger than my calculated area?
Not necessarily. Both sheet dimensions must fit after trying the sheet in either orientation. This calculator checks length and width independently.
Does this calculator design seams or size a waterfall?
No. It checks single rectangular sheets for one pond basin. Waterfalls, islands, complex contours and joined panels need their own measurements and installation plan.