Well Pump Size Calculator
A 2-bathroom home with a 150-foot pumping water level, 40 feet of rise and run to the house and a 40/60 PSI switch needs about 10 GPM against roughly 343 feet of total dynamic head, which our calculator sizes as a 1 HP submersible. A well pump has one job: deliver enough gallons per minute against the total height and pressure it has to push. Size it too small and showers starve when the washer runs; too big and it short-cycles itself to an early death.
Treat the result as a starting point. Installers pick the final pump from manufacturer pump curves using your well's real measurements, so use this to sanity-check quotes, not to order a pump.
Well pump size by pumping water level
Total dynamic head = pumping water level + rise and run to the house + pressure head (cut-off PSI × 2.31) + a pipe friction allowance. For a 2-bathroom home (about 10 GPM) with 40 ft of rise and run and a 40/60 PSI switch:
| Pumping water level | Total dynamic head | Pump size |
|---|---|---|
| 50 ft | about 235 ft | ¾ HP |
| 100 ft | about 289 ft | 1 HP |
| 150 ft | about 343 ft | 1 HP |
| 200 ft | about 397 ft | 1½ HP or larger |
| 300 ft | about 504 ft | 1½ HP or larger |
Calculated with this tool's formula, which allows 7.5% of the pipe run for friction. Guidance only: installers choose the final pump from manufacturer pump curves.
How to calculate well pump size
Flow demand uses the fixture-count method: each fixture (faucet, shower, toilet, appliance) draws roughly 1 GPM, so we estimate fixtures from bathroom count (about 3 per bathroom plus a kitchen/laundry baseline) with an 8 GPM floor — a typical home needs 8–12 GPM at peak, and 6 GPM is the common minimum standard for household supply.
Head uses the standard total dynamic head (TDH) formula: TDH = pumping water level + vertical rise and run to the house + (pressure switch cut-off PSI × 2.31 ft per PSI) + a friction allowance. Converting pressure to feet of head is why the switch setting matters — a 40/60 switch adds 60 × 2.31 ≈ 139 ft of equivalent head. For friction we apply a simple 7.5% allowance on the total pipe run, which approximates Hazen-Williams losses for correctly sized PVC at residential flow rates; long or undersized pipe runs can lose more.
Horsepower guidance follows the widely published residential heuristics: ½ HP handles up to roughly 150 ft of TDH, ¾ HP to about 250 ft, and 1 HP to about 350 ft, with deeper or higher-demand systems stepping to 1½ HP and up. Below about a 100 ft water level a jet pump is an option; beyond that, submersible is the answer. These bands are guidance only — a pro selects the actual model from manufacturer pump curves, matching your measured GPM and TDH to a specific impeller stack, which is exactly what the independent local pros we connect you with do before quoting.
Estimates only — independent local providers quote their own pricing. Data last reviewed 2026-10.
Sources
- Engineering ToolBox — PVC Pipes Friction Loss Tables
- HomeGuide — Well Pump Cost (Aug 7, 2025) (third-party estimate)
Frequently Asked Questions
What size well pump do I need for my house?
Most homes need a pump delivering 8–12 GPM at the system's total dynamic head. Figure about 1 GPM per fixture for demand, then compute TDH: pumping water level + rise to the house + (cut-off PSI × 2.31) + friction. As rough guidance, ½ HP covers up to ~150 ft TDH, ¾ HP to ~250 ft, and 1 HP to ~350 ft.
What is total dynamic head (TDH)?
TDH is everything the pump pushes against, expressed in feet: the vertical lift from the water level in the well, the rise from wellhead to pressure tank, the pressure it must build (each PSI equals 2.31 ft of head), and pipe friction. A 200 ft water level with a 40/60 switch is already over 350 ft of TDH before friction.
Should I get a jet pump or a submersible pump?
Depth decides. Jet pumps sit above ground and work to roughly 100 ft of water level ($400–$1,400 installed); submersibles hang down the well, handle any residential depth, run quieter, and last longer ($1,000–$2,500 installed). Past ~100 ft, submersible is the only real choice.
What happens if my well pump is oversized?
An oversized pump fills the pressure tank too fast and short-cycles — starting and stopping constantly — which burns out the motor years early and can outpace a low-yield well. That's why pros verify sizing against your well's measured yield and actual pump curves before installing, rather than just going a size up.
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