Sizing Guide • Updated 2026
What size sump pump do you need?
Three inputs. Thirty seconds. Know exactly which horsepower rating fits your basement — then see every model that qualifies, sorted by flow rate.
Sump pump sizing chart
The four residential horsepower tiers
| HP Rating | Basement Size | Conditions | Typical GPH@10ft |
|---|---|---|---|
| ⅓ HP | Under 1,000 sq ft | Low to moderate water table, infrequent cycling | 1,400 – 2,600 |
| ½ HP | 1,000 – 1,500 sq ft | Moderate water table, standard Midwest/Northeast | 2,400 – 4,000 |
| ¾ HP | 1,500 – 2,500 sq ft | High water table, clay soils, frequent cycling | 4,000 – 5,500 |
| 1 HP | Over 2,500 sq ft | Very high water table, full perimeter drain | 5,000 – 7,000+ |
Sump pump sizing calculator
Find the right pump for your basement
Answer three questions about your basement. Our sump pump sizing calculator recommends the right HP and shows every model that qualifies — sorted by flow rate, with no brand preference.
Reference
How to read your existing pump's label
HP or Watts
Look for "HP" or "H.P." on the motor label. If you see watts, divide by 746 to convert: 373W = ½ HP. Fractional ratings like 0.33, 0.5, 0.75 are standard.
Model Number
The model number lets you pull the original spec sheet. Search "[Brand] [Model] spec sheet" to find the manufacturer's performance curve and compare it to your requirements.
Manufacture Date
Usually stamped as a date code or serial number. Pumps over 7 years old near failure are better replaced than repaired — even if they're still technically running.
Voltage
Most residential sump pumps are 120V. Some ¾ HP and 1 HP models require a dedicated 20-amp circuit. Verify before purchasing — your electrician can confirm what's available at the pit.
Common questions
What homeowners actually ask about sump pump sizing
Is ½ HP enough for most basements?
For a typical 1,000–1,500 sq ft Midwest or Northeast basement with a moderate water table, yes — ½ HP is the most common recommendation. It handles 2,400–4,000 GPH at a 10-foot head, which covers the vast majority of residential installations. Upsize to ¾ HP if your pit fills faster than every 2 minutes during heavy rain. Also make sure your float switch is calibrated correctly — a mis-set float triggers the pump too late and effectively reduces available capacity.
Can I use a sump pump sizing chart instead of a calculator?
A sizing chart gives you a starting point based on basement square footage alone. A calculator refines that by factoring in soil type, water table, and whether you have interior drains. Use the chart above to orient yourself, then run the calculator to confirm — especially if you have clay soils or a high water table.
Why does my contractor recommend a bigger pump than the chart says?
Contractors often size up one tier as insurance — a pump running at 70% capacity lasts significantly longer than one at 100% (see our maintenance guide for tips that extend lifespan further). That said, oversizing isn't always better: a pump that short-cycles (turns on and off every 15–20 seconds) wears the motor out faster. The sweet spot is one tier above what the chart indicates if you're in a borderline case.
Related guides
Once you know your size
Installation
What to expect when a contractor installs your new pump.
Replacement
Swapping an old pump for a correctly sized new one.
Maintenance
Annual checks that keep a correctly sized pump running at full capacity.
Battery Backup
Add a backup pump rated for the same HP tier as your primary.
Float Switch
The component that triggers your pump — and why it matters for effective sizing.
Sump Pit
Pit dimensions affect how much the pump cycles — a factor in sizing.
Running Constantly
Diagnose why your pump won't stop — often a sizing or float switch issue.
Repair
When repair makes sense vs. replacing with a correctly sized model.
Local sump pump service
Know what you need — now get a fair price on it
Share your sizing result with local contractors and get competing quotes. You already know the specs — they can't upsell you on something you don't need.
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