Pump Head Calculator
A pump head calculator adds static head and friction loss to get total dynamic head: 20 ft of lift plus 5 ft of friction loss gives 25 ft of head.
Pump head calculator formula
A pump head calculator adds the height water must be lifted to the head that pipe friction takes away. Total dynamic head (ft) = static head + friction head loss. The answer is in feet of water. It is the number you read off a pump curve to see whether a pump can deliver the flow you want.
The formula in plain words
Static head is the vertical climb from the water source to the outlet. Friction head is the extra push needed to get water through the pipe, elbows and valves. Add them. A pump that cannot push that far at your flow will deliver less than you need.
Worked examples
These match the calculator exactly.
- Garden pump lifting from a tank: 20 ft static head and 5 ft friction loss
- Total dynamic head: 20 + 5 = 25 ft
- In psi: 25 × 0.433 = about 10.8 psi
- A longer pipe run to a raised tank: 35 ft static head and 12 ft friction loss
- Total dynamic head: 35 + 12 = 47 ft
- In psi: 47 × 0.433 = about 20.4 psi
In both examples static lift is the larger share. Friction is added on top and rises with flow, so a larger pipe reduces it.
Feet of head and psi
| Pressure | Feet of head |
|---|---|
| 10 psi | 23.1 ft |
| 20 psi | 46.2 ft |
| 40 psi | 92.4 ft |
| 60 psi | 138.6 ft |
One foot of water column is about 0.433 psi. Pump curves are drawn in feet, while gauges read psi.
Where friction loss comes from
Friction loss depends on flow, pipe diameter, pipe length and the pipe material. You can find it with the pipe friction loss calculator, which returns psi. Convert that to feet by multiplying by 2.31 and enter it here. Fittings add loss as well, so include them in the friction figure when you know it.
If friction loss turns out to be large, a bigger pipe can cut it. Doubling the diameter of a pipe cuts friction loss by far more than half at the same flow, since the loss falls steeply as diameter rises.
Adding outlet pressure
A sprinkler head, a spray nozzle or a filter may need pressure at the end of the line. This is not in the formula. Convert the required psi to feet and add it. A sprinkler that wants 30 psi adds 30 × 2.31 = 69.3 ft. Then example 1 becomes 25 + 69.3 = 94.3 ft. This is why irrigation pumps are rated for more head than the lift alone suggests.
Reading a pump curve
A pump curve plots head on one axis and flow on the other. As flow increases, the head a pump can deliver falls. Find your total dynamic head on the head axis, then read across to the curve and down to the flow. If that flow matches your need, the pump fits. Choose a pump with some margin and run it near the middle of its curve.
A full example with all three parts
Say a pump lifts water 20 ft to a spray nozzle. Friction in the pipe is 5 ft. The nozzle needs 30 psi.
- Static head: 20 ft
- Friction head: 5 ft
- Nozzle pressure: 30 × 2.31 = 69.3 ft
- Total: 20 + 5 + 69.3 = 94.3 ft
The tool gives the first two parts, 25 ft. The extra 69.3 ft is the part people forget, and it changes which pump is right for the job.
Why a wider pipe helps
Friction head shrinks quickly as pipe diameter grows. A pump that pushes 50 GPM through a 1.5 inch pipe works against much more friction than through a 2 inch pipe, as the velocity numbers on the pipe velocity page show. If your total comes out too high for the pump you have, a larger pipe is often cheaper than a larger pump.
Common mistakes
- Using pipe length as static head. Only the vertical rise counts.
- Forgetting the friction in long runs.
- Leaving out outlet pressure for sprinklers and filters.
- Mixing up psi and feet.
- Sizing the pump for one flow and running it at another.
Related pages
Compute pressure loss with the pipe friction loss calculator. For pools, see the pool pump size calculator. For flow itself, use the flow rate calculator.
Frequently asked questions
What is total dynamic head?
It is the total work a pump must do in feet of water: the vertical lift plus the friction losses in the piping. This calculator adds the two, so 20 ft static head and 5 ft friction loss is 25 ft of total dynamic head.
How do I find static head?
Measure the vertical distance from the water surface at the supply to the point where water leaves the pipe. Distance along the pipe does not count. A pump that raises water 20 ft vertically has 20 ft of static head.
How do I convert psi to feet of head?
Multiply psi by 2.31. 10 psi is 23.1 ft of head and 20 psi is 46.2 ft. Going the other way, multiply feet by 0.433, so 25 ft is about 10.8 psi.
Does the result include outlet pressure?
No. If a nozzle or sprinkler needs a certain pressure, convert it to feet and add it by hand. A 30 psi requirement adds 69.3 ft.
Can I choose a pump from this number alone?
Not quite. Pick a pump whose curve gives the flow you need at this head. Use the maker's data, and ask a supplier or pump professional if the system is large.
Estimates only. Verify quantities with your supplier before purchasing.