Koi Pond Pump Size Calculator
Free Calculator
Estimate the pump flow your koi pond needs
Enter your pond volume and plumbing details to estimate the flow rate your pump should deliver at your system's total dynamic head.
1. Pond circulation
Don't know it? Calculate pond volume first.
One complete pond-volume turnover per hour is a common starting target for koi ponds. Your filter and pond design may call for a different flow.
2. Plumbing and head
Vertical rise from pond water level to the highest discharge point.
Approximate discharge-pipe run from pump to outlet.
Friction is estimated using approximate Schedule 40 PVC inside diameters. Flexible tubing and other pipe types can differ.
Add manufacturer-stated pressure/head loss for filters, UV units, heaters, or other inline equipment if known.
3. Waterfall optional
If this pump also feeds a waterfall, enter its width. The calculator will make sure the design flow is high enough for both circulation and the waterfall.
Pump selection target
Choose a pump that can deliver the target flow at the calculated head.
Pump nameplate flow is usually stated at little or no head. Select from the manufacturer's performance curve at your estimated total dynamic head, not from the zero-head GPH rating alone.
How to size a koi pond pump
Start with the circulation flow your pond needs, then account for the resistance the pump must overcome. The calculator estimates that resistance as total dynamic head (TDH): vertical lift plus friction in the pipe and fittings plus any additional equipment loss you enter.
Circulation flow
Pond gallons × 60 ÷ turnover minutes
Total dynamic head
Vertical + pipe + fittings + equipment
Pump selection
Required GPH at calculated TDH
Why the pump's maximum GPH rating can be misleading
A pump moves less water as the head it works against increases. A pump advertised as 4,000 GPH may deliver substantially less after lifting water several feet and pushing it through pipe, elbows, valves, and filtration. That is why this calculator gives you two numbers to take to a pump performance chart: the required delivered flow and the estimated total dynamic head.
What counts as vertical head?
Measure from the pond's operating water level to the highest point where the pumped water discharges. Do not add horizontal pipe length to vertical head. Horizontal runs create friction instead, which the calculator estimates separately from pipe size, length, and flow.
Calculator note
This is a planning estimate, not a pump-manufacturer performance test. Actual flow depends on the exact pipe or hose inside diameter, fittings, filter condition, valves, equipment, pump curve, and how the system is installed. Verify the final selection against the pump manufacturer's flow-versus-head chart and the flow requirements of your filtration system.