Sump Pump Size Calculator

Estimate the pump capacity and horsepower needed to keep up with water inflow.

sump pit
RECOMMENDED PUMP
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horsepower

Usage Tip

A battery backup pump is cheap insurance against power outages during heavy storms.

THE MATH
GPH = area × rain × 0.623 × safety
Where: rain = peak rainfall (in/hr)  •  GPM = GPH ÷ 60
• 0.623 converts inch-feet to gallons
• Add head pressure for tall lifts
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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.