Pumps are sold by gallons per minute, water meters bill by the gallon or cubic meter, HVAC ducts are sized in cubic feet per minute, rivers are gauged in cubic feet per second and oil wells report barrels per day. All of these are the same quantity — volume moved per unit of time — and this converter moves between them with exact factors.
How to use the flow rate converter
- Enter the flow rate.
- Pick the unit you have in From and the unit you want in To.
- Read the converted value, then the extra rows: how much volume that flow delivers in an hour, a day and 30 days, and how long it takes to fill a 50-gallon tank.
- The table lists the same flow in all 18 units, followed by everyday flows for comparison.
How flow units convert
Every unit is defined as a volume divided by a time, so the conversion factor is the volume ratio divided by the time ratio:
The calculator stores each unit in cubic meters per second, built from exact definitions: a US gallon is 231 cubic inches (3.785411784 L), an imperial gallon is 4.54609 L, a cubic foot is 0.3048³ m³ and an oil barrel is 42 US gallons.
| From | To | Multiply by |
|---|---|---|
| gpm | L/min | 3.785411784 |
| L/min | gpm | 0.264172 |
| ft³/s (cfs) | gpm | 448.831 |
| m³/h | gpm | 4.40287 |
| MGD | gpm | 694.444 |
| ft³/min (cfm) | L/s | 0.471947 |
Worked example
A well pump is rated at 12 gpm.
Liters per minute: 12 × 3.785411784 = 45.42 L/min.
Per day: 12 gal × 60 × 24 = 17,280 gallons, or 65.41 m³, if it ran nonstop.
Fill time: a 50-gallon water heater fills in 50 ÷ 12 = 4.17 minutes.
Second case: a 2.5 gpm showerhead running for a 10-minute shower uses 25 gallons, which is 25 × 3.785 = 94.6 liters.
Flow benchmarks worth knowing
- Faucets and showerheads. US federal rules cap new bathroom faucets at 2.2 gpm and showerheads at 2.5 gpm; WaterSense-labeled fixtures go lower.
- Household supply. A typical home well pump delivers about 6–12 gpm; a whole house with several fixtures open may draw 10–15 gpm.
- Firefighting. A common 1¾-inch attack hose flows around 150 gpm, which is 568 L/min.
- Rivers and canals are measured in cfs. One cfs flowing for a full day delivers almost exactly 2 acre-feet (1.98), a handy figure in irrigation.
Pitfalls
- Volumetric vs. mass flow. This page converts volume per time. Mass flow (kilograms or pounds per hour) depends on density, which changes with the fluid and its temperature.
- Standard vs. actual cfm. Compressed-air and gas equipment often lists SCFM, the flow corrected to standard pressure and temperature. Converting SCFM to L/min with these factors gives standard liters per minute, not the actual volume at line pressure.
- US vs. imperial gallons. British and older Canadian pump specs may use imperial gallons, which are 20% larger.
For plain volumes, use the volume converter or gallons to liters. To find how much a tank holds before working out a fill time, try the tank volume calculator.
Frequently asked questions
How many liters per minute is 1 gallon per minute?
One US gallon per minute is exactly 3.785411784 liters per minute, because a US gallon is defined as 3.785411784 liters. One imperial gallon per minute is 4.54609 L/min.
How do I convert cfs to gpm?
Multiply by 448.83. One cubic foot is about 7.48052 US gallons, and there are 60 seconds in a minute, so 1 ft³/s = 7.48052 × 60 = 448.83 gpm.
What does MGD mean?
Million gallons per day, the unit US water and wastewater utilities use for plant capacity. One MGD equals about 694.44 gallons per minute or 3,785 cubic meters per day.
Is CFM a flow rate for air or water?
Cubic feet per minute is a volume per time, so it works for any fluid. In practice it is the standard unit for air: HVAC airflow, fans, compressors and dust collectors.