Volumetric flow rate measures the volume of fluid passing a point per unit time. The SI unit is cubic metres per second (m³/s), but litres per minute (L/min) and litres per second (L/s) are more practical for everyday plumbing and HVAC work. In the United States, gallons per minute (GPM) is the standard for pump sizing, pipe specification, and irrigation systems.
Cubic feet per minute (CFM = ft³/min) is used in HVAC for air handling unit ratings and ventilation calculations. Engineers convert between units when specifying pumps, valves, and flow meters across metric and imperial systems. A standard residential shower uses roughly 8–10 L/min (2–2.5 GPM); a typical garden hose runs about 20 L/min (5 GPM).
| 1 L/s | = 60 L/min |
| 1 L/min | = 0.2642 GPM |
| 1 GPM | = 3.785 L/min |
| 1 m³/hr | = 4.403 GPM |
| 1 ft³/min | = 7.481 GPM |
| 1 m³/s | = 1000 L/s |