Pond liner size calculator
What size pond liner to buy for a garden pond, from its length, width, depth and edge overlap.
Liner size
Measure length and width at the widest points, even for a curved pond. Buy underlayment the same size as the liner.
How to use it
Enter the pond's length and width at the widest points, its deepest point, and how much liner you want lapped over the edge so it can be buried or held down with stone. One foot on each side is a common choice.
How it's calculated
The liner has to go down one side, across the bottom and up the other, then lap over both edges:
- Liner length = pond length + 2 × depth + 2 × overlap.
- Liner width = pond width + 2 × depth + 2 × overlap.
| Pond | Deepest point | Overlap | Liner |
|---|---|---|---|
| 6 × 4 ft | 1.5 ft | 1 ft | 11 × 9 ft |
| 10 × 8 ft | 2 ft | 1 ft | 16 × 14 ft |
| 15 × 10 ft | 2.5 ft | 1 ft | 22 × 17 ft |
The formula uses the deepest point everywhere, which leaves spare liner over shelves and shallow ends. That's intended: a liner that's slightly too big can be trimmed, but one that's too small can't be stretched.
Tips
- Lay underlayment first, the same size as the liner, to protect it from stones and roots.
- Fill the pond slowly with the liner loose, smoothing folds as the water pulls it into shape.
- Don't trim the overlap until the pond is full and has settled for a day.