Sump Pump Calculator
Size a sump pump from inflow rate, lift height and basin capacity.
About Sump Pump Calculator
Capacity is set above peak inflow so the pump can gain on the water rather than merely keep pace. Cycle frequency matters because excessive starting is what wears the motor out. Pump curves fall steeply with head, so a pump rated at the required flow at zero lift may deliver less than half of it at three metres.
Formula
Sump Pump
Pump capacity = peak inflow × 1.5; total head = lift + friction losses
- total head
- Vertical lift plus friction in the discharge pipe
- cycles
- Starts per hour, driven by inflow and usable basin volume
Worked example
With the default values below, Sump Pump Calculator returns Pump Capacity Required of 60.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Peak water inflowminimum 0.1 L/min
- 40 L/min
- Vertical liftminimum 0 m
- 3 m
- Discharge pipe lengthminimum 0 m
- 12 m
- Basin volumeminimum 1 L
- 70 L
- Pump efficiencyaccepts 10–90 %
- 50 %
Results
- Pump Capacity Required
- 60.00 L/min
- Total Head
- 3.48 m
- Pump Power
- 0.0683 kW
- Pump Cycles per Hour
- 57.1
- Pump Capacity Required
- 15.85 gpm
Step by step
- 1Values used
- 2Sump Pump
- 3Pump Capacity Required= 60.00 L/min
- 4Total Head= 3.48 m
- 5Pump Power= 0.0683 kW
- 6Pump Cycles per Hour= 57.1
- 7Pump Capacity Required= 15.85 gpm
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Sump Pump calculated?
Pump capacity = peak inflow × 1.5; total head = lift + friction losses Capacity is set above peak inflow so the pump can gain on the water rather than merely keep pace. Cycle frequency matters because excessive starting is what wears the motor out.
Why does Sump Pump matter?
Pump curves fall steeply with head, so a pump rated at the required flow at zero lift may deliver less than half of it at three metres.
What values do I need to enter?
This calculator takes 5 inputs: Peak water inflow, Vertical lift, Discharge pipe length, Basin volume, Pump efficiency. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.