Convert flow rates between GPM, LPM, cubic meters per hour, CFM, and liters per second. Uses the exact factor 1 GPM = 3.78541 LPM.
The Flow Rate Converter converts between gallons per minute (GPM), liters per minute (LPM), liters per second (L/s), cubic meters per hour (m³/h), and cubic feet per minute (CFM). These are the standard volumetric flow rate units used in plumbing, HVAC, industrial processes, and water treatment.
Flow rate measures the volume of fluid passing through a point per unit of time. It's critical for sizing pipes, pumps, valves, and HVAC ductwork. The US uses GPM for liquid and CFM for air. Metric systems use LPM, L/s, or m³/h depending on the application and scale.
The core liquid conversion is 1 GPM = 3.78541 LPM (based on 1 US gallon = 3.78541 liters). For air flow, 1 CFM = 28.3168 LPM. This converter handles both liquid and gas flow units for cross-system convenience.
Integrating this calculation into regular planning habits ensures that work priorities reflect actual data about where time and energy produce the greatest results each week.
Plumbers, HVAC technicians, and process engineers regularly convert between US and metric flow rate units. This tool provides instant conversion between all common volumetric flow rate units. Data-driven tracking enables proactive schedule management, helping professionals protect focused work time and reduce the cognitive overhead of constant task-switching throughout the day.
1 GPM = 3.78541 LPM = 0.0630902 L/s = 0.227125 m³/h 1 CFM = 28.3168 LPM = 0.471947 L/s = 1.69901 m³/h 1 m³/h = 4.40287 GPM = 16.6667 LPM = 0.27778 L/s
Result: 37.85 LPM / 2.27 m³/h
10 GPM × 3.78541 = 37.85 LPM. 10 GPM × 0.227125 = 2.27 m³/h. 10 GPM is a typical flow rate for a residential main water line or a medium-sized pump.
Residential plumbing design is based on flow rates. The main water line is sized for peak demand (multiple fixtures running simultaneously). Pipe sizes range from 3/4" (10–15 GPM) to 1" (20–30 GPM) for homes. Commercial buildings use larger pipes and higher flow rates.
Air conditioning systems move air through ducts measured in CFM. A typical residential system moves 400 CFM per ton of cooling. Duct sizing balances flow rate against velocity to minimize noise and pressure drop. Bathroom exhaust fans are rated at 50–150 CFM.
Industrial processes use various flow meters: magnetic, ultrasonic, Coriolis, turbine, and differential pressure. Flow rates range from mL/min in lab settings to thousands of m³/h in water treatment. Accurate flow measurement is critical for process control, billing, and safety.
Multiply GPM by 3.78541. For example, 5 GPM × 3.78541 = 18.93 LPM. To convert LPM to GPM, divide by 3.78541 (or multiply by 0.264172).
A residential main line typically provides 10–25 GPM (38–95 LPM). Individual fixtures need 1.5–3 GPM. Pipe sizing, water pressure, and distance from the meter all affect available flow.
CFM (cubic feet per minute) measures the volume of air flowing per minute. It's the standard unit for HVAC ductwork, ventilation fans, and air compressors in the US. Metric equivalent is m³/h or L/s.
Flow rate, pipe diameter, and velocity are related: Q = A × v (flow = cross-sectional area × velocity). A larger pipe at the same velocity carries more flow. Pipe sizing charts use flow rate and acceptable velocity to determine the needed diameter.
Flow rate (GPM, LPM) is the volume per time. Velocity (ft/s, m/s) is the speed of the fluid. They're related by pipe area: velocity = flow rate / pipe area. The same flow rate through a smaller pipe means higher velocity.
While both are volumetric flow rates, comparing liquid GPM to air CFM directly can be misleading because air is compressible and much less dense. The conversion math is valid, but the practical context differs. 1 CFM air has far less mass than 1 GPM water.