A well pump sizing calculator estimates the required flow rate (GPM) and horsepower for a residential well pump based on fixture count, well depth, and pressure requirements.
How to Size a Well Pump
Well pump sizing starts with determining peak demand flow rate in gallons per minute. Each fixture in a home has an estimated simultaneous use probability, and the pump must meet peak simultaneous demand.
General Sizing Rules
The standard minimum for residential wells is 6 GPM. Most homes with 2-3 bathrooms need 8-10 GPM. Horsepower requirements increase with well depth — deep wells need more pressure head to push water to the surface.
Always hire a licensed well contractor for installation. Actual pump selection depends on well yield, casing diameter, and local regulations.
FAQ
How many GPM do I need for my well pump?
Most homes need 6-12 GPM. Calculate by counting fixture units: each bathroom adds ~1-2 GPM demand. A rule of thumb is 1 GPM per bedroom with a minimum of 6 GPM for comfortable water pressure.
What HP well pump do I need?
Well pump horsepower depends on depth and flow rate. A 1/2 HP pump handles up to 25 GPM at shallow depths. Deep wells (200+ ft) typically need 1 HP or more. This calculator estimates based on your inputs.
What is the difference between jet pump and submersible pump?
Jet pumps sit above ground and use suction — they work for wells under 25 ft (shallow well) or up to 100 ft (deep well jet). Submersible pumps go inside the well casing and push water up, working for any depth.
How do I know if my well pump is undersized?
Signs include: pressure drops during simultaneous use, pump runs continuously, low flow from faucets, air spitting from taps. These indicate the pump cannot keep up with household demand.
Is this calculator free?
Yes, completely free with no signup required.