Flow Rate Converter
Convert GPM, L/min, CFM, m³/h and more. Or calculate flow rate from volume and time, or from a pipe's inner diameter and average fluid velocity.
Calculate or Convert Flow Rate
Select your calculation, enter measurements, and see a result instantly.
Convert a known flow rate between measurement systems. US and UK Imperial gallons are intentionally separate.
Popular flow rate conversions
Calculate the average volumetric flow rate when you know the amount of liquid or gas and the time taken.
Example: 500 L ÷ 10 min = 50 L/min. Elapsed time must be greater than zero.
Estimate volumetric flow through a full circular pipe from its internal diameter and the average fluid velocity.
This geometric estimate assumes the diameter represents the open pipe interior and the velocity is the cross-sectional average. It does not predict flow from pipe pressure, pump rating or friction.
10 US gal/min equals 37.85411784 L/min
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How to Use the Flow Rate Converter
Choose one of the three modes to convert a known flow rate or calculate a flow rate from other measurements. Each mode uses a different type of input.
Convert units
Enter a rate such as 10 US gallons per minute, then choose the destination unit. Edit the To amount if you want to convert backward.
Use volume and time
Enter a measured volume and elapsed time. The tool divides volume by time to calculate an average rate.
Calculate pipe flow
Enter internal pipe diameter and average velocity. The tool multiplies circular cross-sectional area by velocity.
Flow Rate Formulas and Examples
1. Convert one flow-rate unit into another
Every supported unit is expressed in cubic meters per second (m³/s). Multiply by the source unit's factor and divide by the destination unit's factor:
Converted rate = Entered rate × (m³/s per source unit ÷ m³/s per target unit)Example: 10 US gallons per minute × 3.785411784 = 37.85411784 liters per minute. The tool distinguishes US liquid gallons from UK Imperial gallons.
2. Flow rate from volume and time
Volumetric flow rate is the amount of volume passing a point per unit of time. If a container collects 500 liters in 10 minutes, the average flow rate is:
Q = Volume ÷ Elapsed time = 500 L ÷ 10 min = 50 L/min3. Pipe flow rate from diameter and velocity
For a full, round pipe, the flow area is π multiplied by the square of the inside radius. Multiply that area by average fluid velocity. This assumes steady flow through the measured area.
Q = π × (D ÷ 2)² × vExample: For a 100 mm internal diameter and an average velocity of 2 m/s: Q ≈ 0.01570796 m³/s ≈ 15.70796 L/s.
Flow rate is not the same as flow velocity. m³/s is volume per time; m/s is distance per time. The pipe calculator combines the two using cross-sectional area.
Flow Rate Conversion Chart
The chart changes when you choose different units in the main Flow Rate Converter. The displayed values are rounded for readability.
| US gallons per minute (US gal/min) | Liters per minute (L/min) |
|---|---|
| 1 | 3.785411784 |
| 5 | 18.92705892 |
| 10 | 37.85411784 |
The live chart lists 1, 2, 5, 10, 25, 50, 100 and 1,000 source units.
Reference values for all supported units
| Unit | Equivalent in L/s | Typical use |
|---|---|---|
| US gallons per minute (US gal/min) | 0.0630901964 L/s | US liquid gallons per minute |
| US gallons per hour (US gal/h) | 0.00105150327333 L/s | US liquid gallons per hour |
| UK gallons per minute (UK gal/min) | 0.0757681666667 L/s | Imperial gallons per minute |
| Liters per second (L/s) | 1 L/s | Metric volume each second |
| Liters per minute (L/min) | 0.0166666666667 L/s | Metric volume each minute |
| Liters per hour (L/h) | 0.000277777777778 L/s | Metric volume each hour |
| Cubic meters per second (m³/s) | 1000 L/s | SI volumetric flow rate |
| Cubic meters per minute (m³/min) | 16.6666666667 L/s | Metric volume each minute |
| Cubic meters per hour (m³/h) | 0.277777777778 L/s | Water and industrial systems |
| Cubic meters per day (m³/day) | 0.0115740740741 L/s | Water supply and wastewater |
| Cubic feet per second (ft³/s) | 28.316846592 L/s | Water and engineering flow |
| Cubic feet per minute (CFM) | 0.4719474432 L/s | Airflow and ventilation |
| Cubic feet per hour (ft³/h) | 0.00786579072 L/s | Gas and ventilation flow |
Understanding Flow Rate Units
GPM and GPH
US GPM means US liquid gallons per minute, whereas US GPH means US gallons per hour. One US GPM equals 60 US GPH. UK Imperial GPM uses a larger gallon, so 1 UK GPM does not equal 1 US GPM.
Liters and cubic meters per time
One liter is exactly 0.001 cubic meter. One L/s is 60 L/min, and 1 m³/h equals approximately 16.6667 L/min.
CFM, CFS and cubic feet per hour
CFM means cubic feet per minute; CFS means cubic feet per second. These are volumetric flow-rate measurements commonly used for ventilation, airflow and water systems.
Measured vs calculated flow
A volume-over-time measurement estimates average flow. Pipe diameter and velocity can estimate flow if the average velocity is known, but do not give a reliable pump or pressure-based flow prediction by themselves.
Accuracy note: The converter uses defined unit relationships. Real flow calculations depend on measurement accuracy, full-pipe conditions, average velocity and whether the flow is steady. For equipment design, verify data against applicable engineering specifications.
Frequently Asked Questions
How many liters per minute equal one US GPM?
One US liquid gallon is 3.785411784 liters, so one US gallon per minute equals 3.785411784 L/min.
How do I convert CFM to L/s?
Multiply cubic feet per minute by approximately 0.4719474432. For example, 100 CFM is about 47.19474432 L/s.
Are US GPM and Imperial GPM the same?
No. A UK Imperial gallon contains 4.54609 liters, while a US liquid gallon contains 3.785411784 liters. Choose the appropriate gallon definition.
What is the difference between flow rate and water volume?
Volume is the total amount of fluid. Volumetric flow rate describes how much passes a point per unit of time. Examples are 200 liters versus 20 liters per minute.
Can I calculate flow rate from volume and time?
Yes. Divide the measured volume by the elapsed time. For example, 500 L in 10 min gives 50 L/min.
Can I calculate flow rate from pipe diameter?
Not from diameter alone. You also need the average fluid velocity (or another valid hydraulic model). Our Pipe Flow mode takes internal diameter and average velocity.
Should I enter pipe inside or outside diameter?
Use the inside diameter, because flow passes through the open interior cross-sectional area, not the outer pipe dimensions.
Does the pipe calculator account for pressure, friction, and pumps?
No. It calculates flow from an assumed average velocity and diameter. It does not determine velocity from a pump curve, pressure head or friction losses.
Is CFM suitable for both air and water?
CFM is a volume-per-time unit, so it can describe either gas or liquid flow. Real-world measurement and interpretation depend on fluid conditions, especially for gases.
Can the converter display negative flow rates?
This tool accepts non-negative volumetric flow magnitudes. Directional flow can be represented separately when relevant.
Related Calculators
These tools cover related but different measurements; they are not duplicates of flow rate.
Measurement References
US and Imperial volume definitions follow the NIST Guide to the SI, Appendix B.9. The basic volumetric flow equation Q = area × average velocity is explained in the U.S. Department of Energy Fluid Flow Handbook.