How do I calculate pump flow rate?

Pump flow rate is usually given in specifications (GPM or L/min at a certain pressure). To determine required flow: calculate total demand from all fixtures/processes. For filling a tank: Flow rate = Volume / Time desired. Always size pumps with safety margin.

What's the difference between GPM and CFM?

GPM (gallons per minute) measures liquid flow, typically water. CFM (cubic feet per minute) measures gas/air flow. They're both volume flow rates but used in different contexts. For the same volumetric rate, CFM would be used for air, GPM for water.

How does pipe size affect flow rate?

Flow rate = Area × Velocity. Since area = π × r², doubling pipe diameter quadruples the area and potential flow at the same velocity. However, larger pipes cost more and may have lower velocity, affecting sediment transport and pressure loss.

How do I convert between volume and mass flow rate?

Mass flow = Volume flow × Density. For water at room temperature (density ≈ 1 kg/L): 10 L/min = 10 kg/min. For other fluids or temperatures, use the appropriate density. This is important because density changes with temperature and pressure.

Volume Flow Rate Converter

About Volume Flow Rate Conversion

Volume flow rate measures the volume of fluid passing a point per unit time, a fundamental quantity in fluid mechanics and the primary specification for pumps, pipes, and flow systems. Sizing a home water heater, designing an industrial cooling system, calculating ventilation requirements: in each case, volume flow rate sets equipment capacity and system performance.

The SI unit is cubic meters per second (m³/s), but this unit is impractically large for most everyday applications. Practical units like liters per minute (L/min) and gallons per minute (GPM) dominate plumbing and pump specifications. For gas and air systems, cubic feet per minute (CFM) is the standard in HVAC design. Flow rate determines pump sizing, pipe diameter selection, pressure drop calculations, and overall system capacity. The relationship Q = A × v (flow equals area times velocity) connects flow rate to system geometry.

Our converter handles all standard volume flow rate units for plumbing, HVAC, chemical processing, and industrial engineering applications.

Common Volume Flow Rate Conversions

From	To	Multiply By
L/min	GPM (US)	0.2642
GPM (US)	L/min	3.785
m³/h	L/min	16.667
L/min	m³/h	0.06
m³/s	L/min	60,000
CFM (ft³/min)	L/min	28.317
L/min	CFM	0.03531
GPM	m³/h	0.2271
L/s	GPM	15.85
GPM	L/s	0.0631

Volume Flow Rate Unit Reference

Cubic meter per second (m³/s) – The SI unit for volume flow rate. Very large for everyday applications, where 1 m³/s equals 60,000 L/min or about 15,850 GPM. Reserved for large-scale flows: rivers, hydroelectric turbines, major industrial processes, and water supply mains. Most engineering calculations use smaller derived units.

Liter per minute (L/min) – The common practical metric unit for water systems, medical gas equipment, laboratory instruments, and household applications. Easy to visualize: a standard kitchen faucet flows about 8 L/min. Preferred in international standards and most of the world outside North America.

Gallon per minute (GPM) – The US standard for plumbing, pumps, well systems, and flow fixtures. Always refers to US gallons (1 US gal = 3.785 L), not Imperial gallons. Pump curves, fixture specifications, and plumbing codes in the United States use GPM exclusively. A typical shower uses 2-2.5 GPM. A garden hose delivers 5-10 GPM.

Cubic feet per minute (CFM) – The standard unit for air flow in HVAC systems, compressed air systems, ventilation, and dust collection. 1 CFM ≈ 28.3 L/min. Ventilation requirements are specified in CFM, and HVAC equipment is rated accordingly. Vacuum cleaners, air compressors, and fume hoods all use CFM ratings.

Cubic meter per hour (m³/h) – Common metric unit for larger flows where L/min would give unwieldy numbers: industrial processes, water treatment plants, natural gas metering, and cooling towers. 1 m³/h = 16.67 L/min. Often used alongside m³/s in engineering contexts.

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