Flow rate is the volume or mass of fluid passing a point per unit time. This guide covers definitions, units, measurement, conversions, and uses.
What is Flow Rate?
Amount of fluid (liquid or gas) through a cross‑section per time. Critical for water networks, HVAC, and process industries.
Key Concept:
Flow can be volumetric (volume/time) or mass (mass/time). Choose based on application needs.
Common Units of Flow Rate
Volumetric Flow Rate
- m³/s
- L/min
- GPM
- ft³/s
Mass Flow Rate
- kg/s
- lb/hr
- SCFM
- Nm³/h
Measuring Flow Rate
Different instruments suit different media and ranges:
Mechanical
- Turbine
- Positive displacement
- Paddlewheel
Differential pressure
- Orifice plate
- Venturi
- Pitot tube
Electronic
- Ultrasonic
- Magnetic
- Coriolis
Visual methods
- Float meter
- Rotameter
- Weirs/flumes
Flow Rate Conversion Factors
| Unit | m³/s | L/min | GPM |
|---|---|---|---|
| 1 m³/s | 1 | 60,000 | 15,850.3 |
| 1 L/min | 0.0000167 | 1 | 0.2642 |
| 1 GPM | 0.0000631 | 3.7854 | 1 |
Applications of Flow Rate
Residential
- Water supply
- HVAC
- Pool pumps
- Irrigation
Industrial
- Chemical processing
- Oil & gas pipelines
- Pharma
- Food & beverage
Medical
- Ventilators
- Dialysis
- IV fluids
- Anesthesia
Environmental
- Rivers/streams
- Wastewater
- Air quality
- Hydrology
Did You Know?
Amazon River average discharge ≈ 209,000 m³/s (~7,400,000 ft³/s), ~20% of global river outflow to oceans.
Flow Rate in Everyday Life
Household Water Use
- Shower 9.5–19 L/min
- Faucet 4–8 L/min
- Toilet 6–20 L/flush
- Washer 75–150 L/load
Automotive
- Fuel pump ~38 L/min
- Oil pump 20–60 L/min
- Cooling 75–150 L/min
Practical Tip:
When selecting meters, consider medium, range, pipe size, pressure/temperature, accuracy, and whether mass or volume is required.