Sump pump sizing
What size sump pump do I need?
3-step calculator Based on Zoeller & Wayne manufacturer performance curves Reviewed by the WhatSize editorial team
Last reviewed June 2026 • Sources: Wayne Pumps, Zoeller, ASPE Standards
Quick answer
Sump pump size is measured in horsepower (HP) and depends on your pit depth and moisture level. Most basements need a 1/3 HP pump; very deep pits or heavy seepage need 1/2 or 3/4 HP. The 3-step wizard below applies the Zoeller + Wayne manufacturer performance curves to your conditions.
How deep is your sump pit?
Measure from the bottom of the pit to the inlet pipe.
How much water do you get?
Select the option that best matches your basement conditions.
Based on Zoeller + Wayne manufacturer performance curves (GPH vs TDH)
How we picked these products
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Got a result that doesn't match your situation?
Adjust your inputs above and re-run the calculator. Most users find their spec falls within 1-2 sizes of the recommendation.
Formula
HP Class = Moisture Level + Pit Depth → Estimated GPH = Typical Capacity × TDH Adjustment
→ Zoeller & WAYNE manufacturer pump curves at ~10 ft TDH baseline
About this calculation
This is a simplified sizing tool based on published industry standards, not a full professional audit. Critical applications (electrical, HVAC, flooding prevention) require site evaluation by a licensed contractor.
Accuracy depends on your input — subjective factors like dampness level or insulation quality are estimates. Our formulas include a safety buffer that may result in oversizing for some situations (slightly higher cost, but safer than undersizing).
Local variables (climate zone, altitude, insulation levels, building codes) can affect real-world sizing needs. Standards are re-checked quarterly — see our Editorial Policy.
Common scenarios for sump pump sizing
If your situation matches one of these, jump straight to a detailed guide:
Frequently asked questions
What HP sump pump do I need?
1/3 HP handles most residential basements with normal water tables and under 7 ft of total dynamic head. 1/2 HP suits deeper pits (7-12 ft head) or higher water tables. 3/4 HP or 1 HP is for very deep pits or heavy inflow. Reference the GPH vs TDH curve to match your needs.
How many gallons per hour (GPH) do I need?
Match GPH to your pit volume and inflow rate. A typical basement with 30 GPM inflow needs 1,800 GPH minimum (30 GPM × 60 min). Heavy-rain areas or high water tables need 3,000-4,000 GPH. Most residential pumps deliver 2,000-4,000 GPH at 10 ft head.
Pedestal or submersible sump pump?
Submersible: quieter, sealed motor, higher cost, typically 5-15 year lifespan. Best for finished basements. Pedestal: motor sits above water, easier to service, louder, typically 10-25 year lifespan. Best for utility spaces. Both work for typical residential use.
Do I need a battery backup sump pump?
Yes if your area has frequent power outages or your basement floods without power. A battery backup adds 6-12 hours of pumping and runs $150-300. Water-powered backups need municipal water pressure but offer unlimited runtime.