Water Pump Size Calculator

Work out the flow and head your pump needs to move water from the tank, dam or bore to where you want it.

← Back to Calculators

This gives a pump duty estimate only (flow and head) so you can compare it with pump makers' charts. Everything is worked out in your browser. Nothing is saved or sent anywhere.

1. How much water

Choose whether you know the flow you want, or the litres you need to move each day.

A garden hose often runs somewhere around 10 to 20 L/min.
For example a stock trough or a tank top-up.
For a solar pump, about the peak sun hours you get.

2. Lift and pipe

Measure the height from the lowest water level (not the top of the tank) to the highest outlet. Pipe inside diameter is smaller than the size printed on the pipe, so check the pipe maker's chart.

From the lowest water level up to the highest outlet.
Total length of pipe the water runs through.
Inside diameter, not the nominal size.
Extra pipe friction for elbows, valves, tees and filters.
0 to fill an open tank or trough. Sprinklers, taps and houses need more, so check the fitting maker's figure.
Small pumps are often well under 60%. Use the maker's figure if you have it.

Results

How it was worked out

    Before you rely on it

    • This is a pump duty estimate only. Choose a pump whose performance curve gives at least this flow at this total head, and check the maker's limits for suction lift, running dry and water quality.
    • Pipe friction uses the Hazen-Williams formula with C = 140, a typical figure for smooth plastic pipe such as poly or PVC. Older, rough or kinked pipe has more friction.
    • A pump on the surface can only suck water up a limited height (often only a few metres in practice). Deeper water needs a submersible or bore pump. Check the maker's suction lift figure.
    • The wattage is a rough guide to the power drawn. Startup current for mains pumps can be much higher, so check the maker's figures when sizing a generator, inverter or solar.
    • Any work on 240V AC wiring for a pump, including new circuits and outdoor outlets, must be done by a licensed electrician.
    ↑