Private wells · pump head

Well pump total dynamic head calculator.

Add the pumping water level, lift above the ground, friction loss and pressure head to get the total dynamic head a well pump must overcome, then estimate the horsepower for a chosen flow. Runs in your browser; nothing is sent anywhere.

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Planning aid: codes and soils vary by location. Confirm septic and well work with your local health department and a licensed professional.

Inputs

Head components
The level while the pump runs, not the static level.
For example the pressure-switch cut-out.
Friction in the pipe
From the pipe maker’s friction table at your flow.
Horsepower, optional
Read from the pump curve.

Results

Worked example

Pumping water level 120 ft, 10 ft of lift above ground, 50 psi, and 130 ft of pipe at 3 ft of friction per 100 ft. Static head = 120 + 10 = 130 ft. Pressure head = 50 × 2.31 = 115.5 ft. Friction = 3 × 130 / 100 = 3.9 ft. TDH = 249.4 ft. At 10 GPM, water horsepower = 10 × 249.4 / 3,960 = 0.63 hp; at 55% pump and 90% motor efficiency, brake horsepower = 0.63 / (0.55 × 0.9) = 1.27 hp.

Formulas, sources, and limits

Formulas: TDH = total static head + pressure head + friction head (velocity head is usually small and omitted). Total static head = distance from the pumping water level to the ground + vertical lift above the ground to the discharge point. Pressure head = psi × 2.31 ft. Water horsepower = Q × TDH / 3,960 with Q in GPM and TDH in feet. Brake horsepower = water horsepower / (pump efficiency × drive efficiency). Friction head here = loss per 100 ft × pipe length / 100.

Sources (retrieved 2026-10): NDSU Extension AE1057, Irrigation Water Pumps (reviewed Feb. 2022).

Limits: The NDSU publication is about irrigation pumps; the definitions of head and the horsepower equations apply to any pump, but real submersible pump selection needs the manufacturer’s curve at your TDH. Friction per 100 ft is something you must read from a pipe friction table; fittings add loss. The pumping level falls as the pump draws the well down.

Frequently asked questions

What is total dynamic head for a well pump?

The sum of static head (lift from pumping level to the discharge), pressure head, and friction head.

How do I convert psi to feet of head?

Multiply psi by 2.31. For example, 20 psi is 46.2 ft of head.

How much horsepower do I need for a well pump?

Water horsepower is GPM times TDH divided by 3,960; divide by pump and motor efficiency to get brake horsepower. Then pick a standard motor size at or above it.

Is the static water level the same as the pumping level?

No. The pumping level is lower because the water table draws down while pumping.

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