Pond Liner Calculator – What Size Liner Do I Need? | CalcLoft
Find the exact pond liner size you need for any rectangular pond — enter length, width and depth to get the liner dimensions in feet plus the square footage.
How to size a pond liner
A rectangular pond needs a liner big enough to cover the bottom, climb both sides to the deepest point, and leave an overlap that folds under the edging around the rim. Work it out in two steps:
Liner length = pond length + (2 × depth) + (2 × overlap)
Liner width = pond width + (2 × depth) + (2 × overlap)
Depth is doubled because the liner goes down one side, across the bottom and up the other side. For example, a 10 × 6 ft pond with a 2 ft deep point and 1 ft of overlap per side needs a liner length of 10 + 4 + 2 = 16 ft and a liner width of 6 + 4 + 2 = 12 ft — a 16 × 12 ft liner, or about 192 sq ft of material. You will usually trim this from a standard 15 × 20 ft stock liner.
Pond liner size chart (1 ft overlap per side)
The table shows the smallest liner needed for common rectangular ponds at several depths, assuming 1 ft of overlap on every side:
| Pond size (L × W) | Depth 1.5 ft | Depth 2 ft | Depth 3 ft |
|---|---|---|---|
| 8 × 5 ft | 13 × 10 ft | 14 × 11 ft | 16 × 13 ft |
| 10 × 6 ft | 15 × 11 ft | 16 × 12 ft | 18 × 14 ft |
| 12 × 8 ft | 17 × 13 ft | 18 × 14 ft | 20 × 16 ft |
| 15 × 10 ft | 20 × 15 ft | 21 × 16 ft | 23 × 18 ft |
Multiply the two liner dimensions to get the square footage. Pre-cut stock liners commonly come in 10 × 15, 15 × 20 and 20 × 25 ft; anything larger is usually cut to order from a roll.
What size liner for a 10 × 6 ft pond?
A 10 × 6 ft pond with a 2 ft deep point needs a 16 × 12 ft liner (192 sq ft) when you leave 1 ft of overlap per side. That fits inside a standard 15 × 20 ft liner, which you trim to size. The same footprint at 1.5 ft deep only needs a 15 × 11 ft liner. Enter your own numbers in the calculator above.
Related guides
Pond liner calculator FAQ
How much overlap should I leave around the edge?
1 ft per side is usually enough on firm, level ground — it gives you liner to fold under edging rocks or turf. Choose 2 ft when the ground is uneven, you want a wider coping border, or you plan to add a waterfall or stream that shares the liner. Extra liner can be trimmed or folded; a liner that is too small cannot be stretched.
My pond is not a rectangle — how do I measure it?
Measure the longest length, the widest width and the deepest point, then use the rectangle formula above. This deliberately overestimates for free-form ponds — you trim the surplus during installation. Allow a little extra for curves, shelves and any bog or stream area, and remember the liner must follow the deepest profile, not just the water surface.
EPDM or PVC liner — which should I use?
EPDM rubber, usually 45 mil thick, is flexible, puncture-resistant and stable in sunlight, which makes it the standard choice for fish ponds. PVC is lighter and cheaper but usually thinner (about 20–32 mil) and less durable in UV, so it suits smaller decorative ponds where it stays covered. Compare the mil rating and the warranty rather than the brand — with either material, thickness matters more than the name on the box.
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