That pond holds about 2,805 gallons, so it needs a pump of at least 2,900 gph at the height it has to lift the water to the filter or waterfall.
How the pond liner calculator works
PondLinerCalc sizes the liner so it reaches the bottom of the deepest point on both sides and still overlaps the edge: liner length = pond length + 2 × maximum depth + 2 × overlap, and the same for the width. It then rounds each side up to the next 5 ft (or 1.5 m), the steps most EPDM and PVC liners are sold in, and suggests underlayment of the same size. Volume is length × width × average depth, multiplied by π/4 for round or oval ponds, at 7.48 US gallons per cubic foot or 1,000 litres per cubic metre. The pump should turn that volume over once an hour, or twice for koi.
Pond liner sizes for common ponds
Rectangular ponds with a 1 ft overlap each side.
| Pond | Depth | Liner needed | Gallons |
|---|---|---|---|
| 6 × 4 ft | 1.5 ft | 11 × 9 ft | 269 |
| 8 × 6 ft | 2 ft | 14 × 12 ft | 718 |
| 10 × 8 ft | 2 ft | 16 × 14 ft | 1,197 |
| 12 × 10 ft | 3 ft | 20 × 18 ft | 2,693 |
| 15 × 10 ft | 3 ft | 23 × 18 ft | 3,366 |
| 20 × 15 ft | 4 ft | 30 × 25 ft | 8,977 |
Frequently asked questions
Does head height matter?
Yes. Pump ratings fall as the lift increases, so check the flow at your head height on the pump’s chart.
What size pump for a waterfall?
A common rule is about 100–150 gph per inch of waterfall width for a moderate flow.
Can a pump be too big?
A much bigger pump can overwhelm the filter and churn the pond. Match it to the filter’s rated flow.
Is PondLinerCalc free?
Yes, with no sign-up or ads, and your pond details stay in your browser.
Should I buy a bit bigger than calculated?
Yes. Measure the dug hole, not the plan, and round up: a liner that is too small cannot be fixed, while extra can be trimmed.