Pond pump size calculator
Size a pond pump from the pond’s volume and what lives in it. The figure is the flow you need at your actual head height — not the number printed on the box.
Turnover rules
| Pond | Turnover | Flow for 1,000 US gal |
|---|---|---|
| Plants and wildlife, no fish | once every 2 hours | 500 GPH (1,893 L/h) |
| Goldfish and small fish | once an hour | 1,000 GPH (3,785 L/h) |
| Koi | 1.5–2 times an hour | 1,500–2,000 GPH (5,678–7,571 L/h) |
Head height: why the box flow is too high
A pump’s headline flow is measured at 0 ft of head — pumping into nothing. Lifting water to a filter or waterfall, and pushing it through pipe, cuts the flow. Add the vertical lift from the pond surface to the outlet to a friction allowance (roughly 1 ft for every 10 ft of pipe) and read the flow at that head from the pump’s curve. Pick a pump that still delivers the flow above at your head.
The pond pump size chart lists flows for common pond volumes, and the pump sizing guide works through head and pipe size in detail.
Questions
What size pump do I need for a 1,000-gallon pond?
About 1,000 GPH of real flow for goldfish, 500 GPH for a plant-only pond and 1,500–2,000 GPH for koi.
Can a pond pump be too big?
For the fish, rarely — but a pump far larger than the filter can handle pushes water through it too fast to clean, and costs more to run. Match the pump to the filter’s rated flow.
How do I size a pump in litres per hour?
Multiply the pond volume in litres by the turnovers per hour: a 5,000 L goldfish pond needs about 5,000 L/h at the working head.