Well Pump Electrical & Sizing Calculator - HP, Wire Size & Control Box for Residential Wells
Size the pump motor, wire run, control box, and breaker for deep and shallow wells
Free well pump sizing calculator for homeowners, electricians, and well drillers. Enter well depth, static water level, drawdown, desired flow rate, and pipe diameter to calculate total dynamic head and required pump horsepower. Then enter the wire run distance to get the correct wire gauge per manufacturer specifications, circuit breaker size, control box rating, and voltage drop check. Well pump circuits are unique in residential wiring - they run on dedicated 240V circuits with long wire distances, specialized control boxes, and motor characteristics that don't follow standard branch circuit rules. A 1-HP submersible at 300 feet of depth on 400 feet of wire demands careful sizing: undersized wire causes low voltage at the motor, which draws more current to compensate, which causes more voltage drop, which overheats the motor and kills it prematurely. This calculator prevents that death spiral by matching wire size to the actual run length and motor current draw.
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Generator Backfeed Checker →How It Works
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Enter Well Data
Input total well depth, static water level (depth to water when pump is off), and drawdown (how much the level drops during pumping). Your well driller's report has these numbers. If you don't have a report, a static level test with a weighted tape gives you the baseline.
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Specify Flow and Pipe
Enter desired flow rate in GPM and drop pipe diameter. Residential wells typically produce 5-15 GPM. A 1-inch drop pipe handles up to about 10 GPM; 1.25-inch handles up to 20 GPM without excessive friction.
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Calculate Total Dynamic Head
The calculator adds pumping water level, friction loss in the drop pipe, pressure tank target pressure, and elevation differences to get TDH in feet. This determines the required pump HP.
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Enter Wire Run Distance
Measure from your panel to the wellhead horizontally, then add the pump setting depth. This total one-way distance is critical for wire sizing. The calculator uses manufacturer wire sizing tables that account for motor starting current, not just running amps.
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Review Equipment Specifications
Get pump HP, wire gauge, breaker size, control box rating, and a check on voltage drop. If drop exceeds 5%, the calculator recommends the next wire size up.
Built For
- Homeowners replacing a failed well pump and verifying the existing wire is adequate
- Well drillers specifying pump and wire for new residential installations
- Electricians running a new circuit to a well after the existing wire is damaged
- Rural property owners adding a well for a second dwelling or shop
- Property buyers evaluating the adequacy of an existing well system before purchase
Frequently Asked Questions
Learn More
Why Your Well Pump Trips the Breaker
Well pump breaker trips are usually caused by undersized wire, voltage drop on long runs, failing capacitors, or a pump drawing too many amps. How to diagnose the real problem before replacing the pump.
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How to size water storage for fire flow, equalization, and emergency reserve. Elevated vs ground storage tradeoffs, ISO requirements, and cold-climate dead storage.
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