Pump head (H) is the energy added to the fluid per unit weight, expressed in meters (m) or feet (ft). It represents the height the pump can raise the fluid against gravity, including friction and pressure losses.

What is the pump flow formula?

The hydraulic power relationship is: P_hydraulic = ρ × g × Q × H, where ρ is fluid density, g is gravitational acceleration, Q is flow rate, and H is head. Shaft power = P_hydraulic / η, where η is pump efficiency (0–1).

What fluid density is assumed?

The calculator uses the density of water at 20 °C: 998.2 kg/m³ (metric) or 62.3 lb/ft³ (imperial). For other fluids, results scale linearly with the density ratio.

How do I convert GPM to m³/s?

1 US gallon per minute (GPM) = 6.309 × 10⁻⁵ m³/s. The calculator converts internally when you switch unit systems.

What efficiency value should I use?

Typical centrifugal pump efficiencies range from 60% to 85%. Use the manufacturer's pump curve value for your operating point, or enter 100% for theoretical hydraulic power (no shaft losses).

Pump Flow Calculator

Name: Pump Flow Calculator
Availability: InStock
Author: Nham Vu

Solve for pump flow rate, head, shaft power, or efficiency — enter any three values and get the fourth instantly in metric or imperial units.

Pump Parameters

Select what to solve for and enter the three known values.

Unit System

Solve For

Flow Rate (Q)

m³/s

Total Head (H)

Shaft Power (P)

Pump Efficiency (η)

Enter values on the left and click Calculate

Summary

Solve for pump flow rate, head, shaft power, or efficiency — enter any three values and get the fourth instantly in metric or imperial units.

How it works

Select your unit system: Metric or Imperial.
Choose which variable to solve for: Flow Rate, Head, Power, or Efficiency.
Enter the three known values in the corresponding fields.
Click Calculate to get the unknown value instantly.
Use the Reset button to clear inputs and start a new calculation.

Use cases

Size a centrifugal pump for a water supply system.
Verify pump efficiency against manufacturer specifications.
Calculate required motor power for a given flow rate and head.
Convert pump performance data between metric and imperial units.
Check hydraulic power requirements for irrigation systems.
Estimate energy consumption of industrial pumping systems.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu