Flow Rate Unit Converter
Volumetric flow rate measures the volume of fluid passing a point per unit time. Different industries favor different units: plumbers and irrigation engineers use US gallons per minute (GPM), European process engineers use cubic meters per hour (m3/h), HVAC professionals use cubic feet per minute (CFM), and medical device engineers use liters per minute (L/min). This converter handles all the common flow rate units and uses the exact NIST definition of the US gallon (3.785411784 L exactly).
Flow rate conversion factors (referenced to L/min)
1 GPM = 3.78541 L/min = 0.22713 m3/h = 0.13368 CFM = 0.06309 L/s = 6.309e-5 m3/s
All conversions route through liters per minute. The US gallon is exactly 3.785411784 liters. One cubic foot equals exactly 28.316846592 liters.
Flow rate unit applications
- GPM: US plumbing, well pumps, irrigation systems, water heater ratings, EPA WaterSense fixtures.
- L/min: Medical devices (oxygen delivery, dialysis), European and international pump specifications.
- m3/h: European HVAC, industrial process engineering, water treatment plants.
- CFM: HVAC air handling, compressor output, ventilation fan specifications in North America.
- L/s: Civil and hydraulic engineering (drainage, open channel flow).
Flow rate converter: frequently asked questions
How do I convert GPM to L/min?
Multiply gallons per minute (GPM) by 3.785411784 to get liters per minute. One US gallon equals exactly 3.785411784 liters by NIST definition. So 10 GPM = 37.85 L/min.
What is the difference between CFM and L/min?
CFM (cubic feet per minute) is a volumetric flow rate for gases and air, common in HVAC and compressor specifications. One CFM equals 28.3168 L/min. L/min is the SI-adjacent unit used in pump and medical device specifications.
What does m3/h measure and where is it used?
Cubic meters per hour (m3/h) measures volumetric flow. It is the standard unit in European industrial process engineering, water treatment, and HVAC. One m3/h equals 16.6667 L/min or 4.4029 GPM.
What is a gallon per minute used for?
GPM (US gallons per minute) is the dominant flow unit in North American plumbing, irrigation, pump specifications, and water treatment. Well pumps are rated in GPM, and shower heads have EPA WaterSense flow limits in GPM.
How do I convert L/s to m3/h?
Multiply liters per second by 3.6 to get cubic meters per hour. This is because 1 L/s x 3,600 s/h = 3,600 L/h = 3.6 m3/h. The converter also supports L/s as an input unit.
Official sources
- NIST Special Publication 811: Guide for the Use of the International System of Units (SI).
- NIST Handbook 44: US volume unit definitions.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.