Water Horsepower (WHP) Calculator
Calculate water horsepower (WHP) easily using flow rate and head. Find the true hydraulic power needed to move water efficiently in pumps and irrigation systems.
water horsepower calculator:
The Water Horsepower Calculator takes a few seconds to convert flow rate and head into water horsepower (WHP), the pure hydraulic power needed to pump water. The flow rate (GPM) and head (ft), and the tool calculates automatically the WHP on the formula WHP = (Q × H × SG)/3960. It is perfect for choosing the pump capacity, analyzing the use of energy, and the design of water systems.
water horsepower Tool Formula:
The Water Horsepower (WHP) Calculator determines the actual hydraulic power required to move water through a system. WHP is the theoretical horsepower needed by a pump to lift or move water at a given flow rate (Q) and total head (H). The standard formula is:
\[ WHP = \frac{Q \times H \times SG}{3960} \]
where Q = flow rate in gallons per minute (GPM), H = head in feet, and SG = specific gravity of fluid (for water, SG = 1). This tool helps engineers and technicians estimate pump performance, system efficiency, and energy requirements before installation. It’s widely used in irrigation, fire-fighting, and water treatment applications.
Work & Installation — Input to Output Summary
Inputs:
- Flow rate (Q) — in GPM, L/s, or m³/h
- Total head (H) — in feet or meters
- Specific gravity (SG) — default 1.0 for water
- Convert all units into standard GPM and feet.
- Apply the formula:
\( WHP = \frac{Q \times H \times SG}{3960} \) - The result gives hydraulic horsepower.
- If you need brake horsepower (BHP), divide WHP by pump efficiency (η):
\( WHP = \frac{WHP}{\eta} \)
Output:
- Water Horsepower (WHP)
- Optional: Brake Horsepower (BHP) and efficiency (%)
- Conversion notes (metric ↔ imperial)
Applications: pump design, fluid power systems, irrigation, and HVAC water circuits.
Testing and Final Adjustments
Upon calculation, compare the values of WHP with the pump curves provided by the manufacturer to ensure that the actual performance is present. Commissioning Measure real flow and real head with a flow meter and pressure gauge. When the observed flow is less than expected, then it could be due to friction losses or improper sizing of pipes. Check the efficiency of the pump and brake horsepower (motor load reading) against the calculated WHP. Tune discharge valves or impeller trims to perfection. Make sure that the suction lift, temperature, and fluid properties are the same as the design conditions. Periodic testing can be used to minimize losses of energy, keep the systems stable, and increase the life of the pumps. Record all readings taken in the process of hydraulic testing and also ensure safety measures are taken.
Frequently Asked Questions - Water Horsepower (WHP) Calculator:
What is water horsepower (WHP)?
Water horsepower is the theoretical power required to move water at a specific flow rate and head, excluding pump losses.
What is the WHP formula?
WHP = (Flow × Head × Specific Gravity) / 3960 when flow is in GPM and head in feet.
Why divide by 3960 in the WHP formula?
3960 is a constant that converts GPM × ft-lbf/min to horsepower.
How do you find brake horsepower (BHP)?
Divide WHP by pump efficiency: BHP = WHP / η.
Can this calculator be used for fluids other than water?
Yes, adjust specific gravity (SG) to match the fluid’s density.
What are common WHP units?
WHP is measured in horsepower (HP), though metric conversions to kilowatts (kW) are possible.
How accurate is WHP compared to BHP?
WHP is theoretical; actual BHP is higher due to pump and motor inefficiencies.
What if flow is in L/s or m³/h?
Convert to GPM before applying the formula or use a built-in converter.
How does pump efficiency affect WHP?
Higher efficiency reduces the required input power to achieve the same WHP.
Why use WHP in system design?
It helps determine pump sizing, energy costs, and hydraulic system performance.
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