Figure out what size well pump you need for your home or homestead. Enter your well specs, household demand, and outdoor water uses to get the required GPM, Total Dynamic Head, recommended horsepower, pressure tank size, and electrical requirements.
Enter animal counts. Demand is calculated based on waterer fill rate — the pump must be able to refill waterers fast enough throughout the day.
Sizing a well pump comes down to two numbers: how many gallons per minute (GPM) your household and property need at peak demand, and how hard the pump has to work to push water from the bottom of the well up to your pressure tank — a measurement called Total Dynamic Head (TDH), expressed in feet. Get those two numbers right and you can match them to a standard pump curve to find the correct horsepower.
GPM is straightforward to estimate. Each bathroom in a home represents a peak demand of roughly 3–5 GPM, accounting for the possibility that a toilet might flush while a shower runs and someone is at the sink. The national standard most pump contractors use is 3–5 GPM per bathroom; this calculator uses 4 GPM as the default midpoint. Irrigation zones add 1–3 GPM each depending on whether you're running sprinkler heads or drip line. The goal is not to calculate what you use on an average day — it's to handle the single worst-case peak moment, because that's when the pump must perform or the pressure drops.
Total Dynamic Head is the sum of three components. The first is static water level — the depth from the surface to the top of the water in your well when the pump is off. The second is the drawdown — as the pump runs, the water level drops, so the pump has to lift water from deeper than the static level. The pump set depth (where the pump physically sits) is the maximum lift distance and is what this calculator uses. The third component is pressure head: the energy needed to push water to your target system pressure. At 50 PSI, that's 50 × 2.31 = 115.5 feet of head. Finally, pipe friction losses — typically estimated at 10% of the vertical lift — are added. A 200-foot set depth pump running to a 50 PSI pressure target has a TDH of roughly 200 + 20 (friction) + 115 = 335 feet.
Once you have GPM and TDH, horsepower follows from standard pump performance curves. A 0.5 HP submersible handles up to about 10 GPM at 100 feet TDH. A 1 HP pump handles 15–25 GPM at 150–250 feet TDH. A 1.5 HP pump is the sweet spot for most homesteads with moderate livestock and a deeper well (250–350 ft TDH). Two HP and above are for high-demand properties, large livestock operations, or very deep wells exceeding 400 feet TDH. Always round up one size — an undersized pump runs continuously, heats up, and fails early.
For any well deeper than about 25 feet, a submersible pump is almost always the right answer and has been the standard for residential wells for decades. Submersible pumps sit directly in the water at the bottom of the well. Because they push water up rather than pulling it, they're not limited by suction lift and can operate at virtually any practical well depth. They also run quieter, require no priming, and are sealed against the elements — the motor is cooled by the water around it. The only downside is that pulling a submersible pump for service requires lifting the entire drop pipe string, which is a job for a pump contractor.
Shallow well jet pumps sit above ground and use suction to draw water up from the well. They're inexpensive, easy to service, and work fine for wells shallower than about 25 feet. Beyond that depth, the physics of suction lift — limited by atmospheric pressure to about 25 feet at sea level, and less at elevation — make them unreliable. At high altitude, shallow well jet pumps may be limited to as little as 20 feet of practical lift.
Deep well jet pumps are a hybrid: the jet ejector assembly goes down into the well, while the motor stays above ground. This extends the practical range to about 100 feet. They're more common in older installations or where the homeowner wants an above-ground pump for easy access. However, they're less efficient than submersibles at the same depth and require careful two-pipe installation to the ejector. For new installations in wells deeper than 50 feet, a submersible is almost universally the better choice.
A jet pump sits above ground (in a pump house or basement) and uses suction to draw water out of the well. Shallow well jet pumps work to about 25 feet; deep well jet pumps use an ejector nozzle in the well and can reach about 100 feet. A submersible pump sits submerged at the bottom of the well and pushes water up through the drop pipe. Submersibles are more efficient, handle deeper wells (hundreds of feet), require no priming, and are the standard choice for virtually all new residential well installations. Jet pumps are simpler to service yourself but are limited by suction physics. If your well is deeper than 25 feet and you're installing new, use a submersible.
Your well yield (in GPM) should be in your original well driller's completion report, which was filed with your state when the well was drilled. If you can't find that document, contact your county health department or state groundwater agency — most states maintain a public database of well logs searchable by address or well ID number. If no record exists, a licensed pump contractor can perform a pump test: they run the well at a controlled rate while monitoring water level drop over time, then calculate a safe yield based on how quickly the aquifer recovers. Never size a pump that exceeds your well's tested yield — if you pump faster than the aquifer recharges, you'll pump the well dry and risk burning out the pump motor.
The pressure tank's job is to store a supply of pressurized water so the pump doesn't have to cycle on and off every time you open a faucet. Short-cycling (the pump turning on and off every few seconds) is the fastest way to kill a pump motor, so the tank needs to hold enough water to satisfy small draws without triggering the pump. The rule of thumb is to size the tank for at least 1 gallon of draw-down capacity per GPM of pump flow rate, which corresponds to roughly 1 minute of pump runtime per cycle. Practical tank sizing: a 20-gallon pressure tank is the minimum for a system up to 5 GPM; a 32–44 gallon tank for 5–15 GPM; an 80-gallon tank for 15–25 GPM; 119+ gallons for larger homestead systems or high-use properties. Larger tanks are always better — they reduce pump cycling, extend pump life, and give you more water reserve during power outages.
A quality submersible pump from a reputable manufacturer — Franklin Electric, Grundfos, Goulds — should last 15–25 years under normal residential use. Shorter lifespans (8–12 years) are common when the pump is undersized for the demand (it runs too much), the well produces sandy or gritty water that wears the impellers, the pump runs dry repeatedly (pumping a well beyond its yield), or voltage fluctuations damage the motor. Signs of a failing pump include reduced water pressure, air or sputtering from faucets, the pump running continuously without building pressure, and unusually high electric bills. Pressure tanks typically last 5–15 years depending on whether the pre-charge bladder maintains its air charge — a waterlogged tank (fully water-filled with no air cushion) causes rapid short-cycling that will kill a good pump within months. Check your tank's air charge annually by pressing the Schrader valve on the tank; it should read 2 PSI below your cut-in pressure (typically 38 PSI for a 40/60 switch).