Well Pump Calculator

Sizing a well pump means matching two things: how much water the house demands at peak, and how hard the pump must work to deliver it. Peak demand is estimated from bathroom count — a common rule of thumb starts around `6` GPM for a one-bathroom home and adds roughly `2` GPM per additional bathroom, standing in for the fixtures likely to run at once.

The work side is total dynamic head — the vertical distance the pump lifts water plus the pressure it must maintain at the house. Depth is added directly in feet, and system pressure converts at `2.31` feet of head per psi. With flow and head known, water horsepower follows from the hydraulic identity GPM times head divided by `3,960`, and dividing by the pump-and-motor efficiency gives the brake horsepower the motor must actually produce.

Treat every number here as a planning estimate. Real well yield, pipe friction, drawdown, and pressure-tank settings all shift the answer, and an undersized or oversized pump both cause problems. Use this to shop and to sanity-check a quote, then have a licensed pump professional size and select the actual unit for your well.