Sump Pump Size Calculator
Find the perfect pump size quickly with our sump pump size calculator. Avoid flooding and improve drainage efficiency with accurate calculations.
Calculate Required HP
How to Use Sump Pump Size Calculator
Follow these simple steps to use the sump pump size calculator:
- Step 1: Measure Water Inflow Rate: Calculate how much water enters the sump pit (in gallons per minute or GPM).
- Step 2: Determine Vertical Lift (Head): Measure the vertical distance from the sump pit to the discharge point (in feet).
- Step 3: Identify Pipe Length: Measure the total horizontal pipe length used for discharge.
- Step 4: Input Data into Calculator: Enter your flow rate (GPM), total head (feet), and efficiency.
- Step 5: Review Recommended Pump Size: The calculator suggests the required horsepower (HP). Always choose a slightly higher capacity pump for safety.
How to Calculate Sump Pump Size
Use this simple formula:
Where:
- Flow Rate = gallons per minute (GPM)
- Total Head = vertical lift + friction loss (feet)
- Efficiency = typically 0.5 to 0.7
Step-by-Step Example
Let's find the recommended pump size with the following details:
- Flow Rate = 40 GPM
- Vertical Height = 10 ft
- Estimated Friction Loss = 5 ft
- Efficiency = 0.6
Step 1: Calculate Total Head
Total Head = Vertical Height + Friction Loss
Total Head = 10 + 5 = 15 ft
Step 2: Apply Formula
Pump Power = (40 × 15) / (3960 × 0.6)
Step 3: Solve
Pump Power = 600 / 2376 ≈ 0.25 HP
Final Result:
You need at least a 0.25 HP sump pump. For safety, choose a 0.33 HP or 0.5 HP pump.
Sump Pump Size Conversion Chart
Note: Values are approximate and assume average efficiency.
| Flow Rate (GPM) | Total Head (ft) | Recommended Pump Size (HP) |
|---|---|---|
| 20 | 10 | 0.16 HP |
| 30 | 10 | 0.20 HP |
| 40 | 15 | 0.25 HP |
| 50 | 15 | 0.33 HP |
| 60 | 20 | 0.50 HP |
| 80 | 20 | 0.75 HP |
| 100 | 25 | 1.00 HP |
Frequently Asked Questions (FAQs)
Most homes need a 1/3 HP or 1/2 HP sump pump. Use a sump pump size calculator for accuracy.
Measure water inflow (GPM) and total head, then apply the pump power formula.
Not always. Oversized pumps cycle too frequently and reduce lifespan.
Total head includes vertical lift and pipe friction losses.
It provides reliable estimates when you input correct measurements.
No. Heavy rainfall or flooding may require a higher-capacity pump.
It may fail to remove water quickly, causing flooding and damage.
Use 0.6 (60%) as a standard estimate for most residential pumps.
Yes. Longer pipes increase friction loss and require more power.
Yes. A backup pump protects your home during power outages or pump failure.