Well Pump Sizing Calculator
Calculate the minimum GPM flow rate needed from your well pump to meet household and livestock water demands, and check if your well can keep up.
How Well Pumps Are Sized Well pumps are rated in GPM (gallons per minute). Peak demand — the simultaneous use of multiple fixtures — determines the minimum pump capacity needed, not average daily use.
Typical Peak Demand by Fixture Shower: 2-3 GPM. Faucet: 1-2 GPM. Toilet flush: 1.6 GPM. Dishwasher: 1-2 GPM. Washing machine: 3-5 GPM. Outdoor hose: 5-10 GPM.
Well Recovery Rate The well must supply water fast enough that it does not run dry during peak use. If your well only recovers at 2 GPM, you need a storage tank (pressure tank or cistern) to buffer demand. Wells with less than 1 GPM recovery often require a large cistern.
Pressure Tank Role A pressure tank stores a few gallons under pressure to reduce pump cycling. It does NOT replace adequate GPM — it just smooths short bursts. A 44-gallon tank only stores about 12-14 gallons of usable water.