What is the Pump Power Calculator?
Calculate pump hydraulic power, shaft power, and motor sizing with this free pump power calculator. Use P = ρgQH for hydraulic power from flow rate and total head, add pump efficiency for brake power, and motor efficiency for input power. Pressure-rise mode uses P = QΔP. Results in kW, hp, and W with daily kWh estimate. Water (SG=1) or custom specific gravity. US formula HP = Q×H×SG/3960 for GPM and ft. Metric and imperial units. Runs instantly in your browser.
How to use the Pump Power Calculator
- Choose Hydraulic Power, Shaft Power, Motor Power, or From Pressure Rise.
- Select metric or imperial units.
- Enter volumetric flow rate (L/s, GPM, m³/hr, etc.) and total head or pressure rise.
- Add pump and motor efficiency for shaft or motor sizing modes.
- Review hydraulic, shaft, and motor power in kW and hp with calculation steps.
Common use cases
- Sizing a motor for a water transfer pump
- Estimating electricity use for a booster pump station
- Checking if an existing pump has adequate power for higher head
- Quick hp calculation from GPM and feet of head on site
- Hydraulics coursework on pump power and efficiency
Frequently asked questions
- How do I calculate pump hydraulic power?
- Hydraulic power P = ρgQH, where ρ is fluid density, g is gravity, Q is volumetric flow rate (m³/s), and H is total head (m). For water, P(kW) ≈ Q(L/s) × H(m) × 9.81 / 1000.
- What is the US pump horsepower formula?
- Hydraulic hp = Q(GPM) × H(ft) × SG / 3960, where SG is specific gravity (1 for water). Shaft hp = hydraulic hp / pump efficiency.
- What efficiency should I use?
- Centrifugal water pumps are often 65–85% efficient depending on size and duty point. Motors are typically 85–95%. Use manufacturer curves for accurate values; presets help with quick estimates.
- Can I calculate power from pressure instead of head?
- Yes. P_hyd = Q × ΔP when ΔP is in pascals and Q in m³/s. Pressure-rise mode accepts kPa or psi and shows equivalent head.
- What is shaft vs motor power?
- Shaft (brake) power is what the pump impeller needs: P_shaft = P_hyd / η_pump. Motor input power accounts for motor losses: P_motor = P_shaft / η_motor.
