Flow Rate Converter
Convert GPM, CFM, L/min, m³/h and the other flow rate units at once.
The size of each unit in liters per second is listed below. Each unit is a volume divided by a time, taken from the volume and time definitions. The converter first turns your flow rate into liters per second, then divides by the size of each unit.
| Unit | Size of one unit | Definition and source |
|---|---|---|
| Metric (SI) | ||
| m³/s (cubic meters per second) | 1,000 L/s | SI unit of volume flow rate |
| m³/min (cubic meters per minute) | 50/3 L/s (about 16.66667 L/s) | 1 m³ ÷ 60 s |
| m³/h (cubic meters per hour) | 5/18 L/s (about 0.2777778 L/s) | 1 m³ ÷ 3,600 s |
| L/s (liters per second) | 1 L/s | 1/1,000 m³ per second |
| L/min (liters per minute) | 1/60 L/s (about 0.01666667 L/s) | 1 L ÷ 60 s |
| L/h (liters per hour) | 1/3600 L/s (about 0.0002777778 L/s) | 1 L ÷ 3,600 s |
| Metric (milliliter) | ||
| mL/min (milliliters per minute) | 1/60000 L/s (about 0.00001666667 L/s) | 1/1,000 L per minute |
| US customary and imperial | ||
| ft³/s (cubic feet per second) | 28.316846592 L/s | 1 ft³ (28.316846592 L) per second. NIST SP 811 |
| ft³/min (CFM, cubic feet per minute) | 0.4719474432 L/s | 1 ft³ per minute. CFM is a common abbreviation. NIST lists 4.719 474 E−01 L/s. NIST SP 811 |
| US gal/min (US GPM) | 0.0630901964 L/s | 1 US gallon (3.785411784 L) per minute. GPM is a common abbreviation. Not the same as the imperial gallon per minute. NIST lists 6.309 020 E−02 L/s. NIST SP 811, NIST Handbook 44 |
| Imperial gal/min (UK GPM) | 454609/6000000 L/s (about 0.07576817 L/s) | 1 imperial gallon (4.54609 L) per minute. About 20% more than the US gallon per minute. NIST SP 811 |
The calculation uses exact fractions, and the only rounding is the one applied when a value is displayed.
US gallons and imperial gallons are different
- US gal/min (US GPM) uses the US gallon, exactly 3.785411784 L (231 cubic inches). Imperial gal/min (UK GPM) uses the imperial gallon, exactly 4.54609 L. The imperial gallon is about 20% larger, so 1 imperial GPM is about 1.2009 US GPM.
- "GPM" alone is ambiguous. Without a note, treat it as the US gallon per minute only if the source is American. This tool lists the two as separate units so you can pick the right one.
- CFM (cubic feet per minute) is a common abbreviation for ft³/min, with 1 ft³ = 28.316846592 L. It is often used for airflow. This tool converts the volume per time as a number; it does not account for air temperature, pressure or density.
- This tool converts volume flow rate only. It does not convert flow velocity (m/s) or mass flow rate (kg/s), which need the pipe size or the density. For tanks, use the Tank Fill & Drain Time Calculator; for volumes themselves, the Volume Converter.
Examples
- 1 US GPM = 3.785411784 L/min = about 0.2271247 m³/h
- 50 US GPM = about 189.2706 L/min
- 1 L/min = about 0.2641721 US GPM
- 100 CFM = about 169.9011 m³/h = about 47.19474 L/s
- 1 imperial GPM = 4.54609 L/min = about 1.20095 US GPM
- 1,000 L/min = 60 m³/h
Notes
- You can enter decimals (up to 12 digits before the decimal point and 6 decimal places). Use a period as the decimal separator. Commas are accepted only as thousands separators, for example 1,234.5. Negative values cannot be entered.
- The conversions are for reference. For equipment such as pumps and fans, use the flow rate and unit stated on the manufacturer's data sheet, and check whether the figure is at a given pressure or head.
Sources
The definitions on this page come from the sources below (checked on November 1, 2026). In NIST SP 811 Appendix B.8, the rows for cubic foot per minute (4.719 474 E−04 m³/s), gallon (U.S.) per minute (6.309 020 E−05 m³/s), gallon (U.S.) (3.785 412 E−03 m³) and gallon (U.K.) (4.546 09 E−03 m³, marked exact) were read word for word; the definition "1 gallon = 231 cubic inches" comes from the NIST Handbook 44 Appendix C text, which was opened and searched (it also gives 1 cubic yard = 27 cubic feet). The figure 3.785411784 L is worked out from 231 cubic inches and the inch (0.0254 m); it was not found as a printed number in the Handbook text. The B.8 table does not mark the cubic foot and US gallon rows as exact; the exact figures here come from the foot (0.3048 m) and the 231 cubic inch definition. Cubic meters, liters, minutes and hours are the standard SI and accepted units.
- NIST Special Publication 811, Appendix B.8: Factors for units listed alphabetically
- NIST Handbook 44, Appendix C: General tables of units of measurement (2026 edition)
Frequently asked questions
How many liters per minute is one GPM?
For the US gallon, 3.785411784 L/min. For the imperial gallon, 4.54609 L/min.
How many m³/h is 100 CFM?
About 169.9011 m³/h.
How many GPM is 1 L/min?
About 0.2641721 US GPM (or about 0.2199692 imperial GPM).
Is GPM the same in the US and the UK?
No. They use different gallons, so the same number of gallons per minute is a different flow rate.