In short: 10 US GPM equals 37.85 L/min, 0.631 L/s, 2.271 m³/h, 1.337 CFM and 8.327 imperial GPM. GPM (gallons per minute) is the standard US unit for water flow rate — enter any value above to convert it both ways.
These are exact unit conversions, not measurements — the accuracy of your result depends on the accuracy of the flow rate you enter.
How to convert GPM to other flow rate units
Flow rate is volume moved per unit of time, so converting between flow rate units is really converting between a volume unit and a time unit at once. The calculator converts your entered value to liters per second internally, then re-expresses that single number in every other unit.
Worked example. Take 10 US GPM. Multiply by 0.0630902 to get 0.630902 L/s. From there: ×60 gives 37.854 L/min; ×3.6 gives 2.271 m³/h; ÷0.471947 gives 1.337 CFM; ÷0.0757682 gives 8.327 imperial GPM. Every figure in the calculator above comes from that same chain of exact conversion factors.
US gallon vs. imperial gallon. A US gallon (3.785 L) is smaller than an imperial or UK gallon (4.546 L), so US GPM and imperial GPM are genuinely different units for the same flow — not just a labeling difference. Always check which gallon a spec sheet means before comparing numbers.
GPM conversion chart
Common US GPM values converted to every unit this calculator supports.
| US GPM | L/min | L/s | m³/h | CFM | cfs | Imperial GPM |
|---|---|---|---|---|---|---|
| 1 | 3.785 | 0.0631 | 0.2271 | 0.1337 | 0.00223 | 0.8327 |
| 5 | 18.927 | 0.3155 | 1.1356 | 0.6684 | 0.01114 | 4.1634 |
| 10 (default) | 37.854 | 0.6309 | 2.2712 | 1.3368 | 0.02228 | 8.3267 |
| 25 | 94.635 | 1.5773 | 5.6781 | 3.3420 | 0.05570 | 20.8169 |
| 50 | 189.271 | 3.1545 | 11.3562 | 6.6840 | 0.11140 | 41.6337 |
| 100 | 378.541 | 6.3090 | 22.7125 | 13.3681 | 0.22280 | 83.2674 |
| 500 | 1,892.706 | 31.5451 | 113.5624 | 66.8403 | 1.11400 | 416.3371 |
| 1,000 | 3,785.412 | 63.0902 | 227.1247 | 133.6806 | 2.22801 | 832.6742 |
Worked examples
Low-flow showerhead
7.57 L/min
A WaterSense-labeled showerhead capped at 2 GPM converts to 7.57 L/min, or 0.126 L/s — useful when comparing US fixture ratings to metric plumbing codes.
Kitchen faucet
5.68 L/min
A standard 1.5 GPM kitchen faucet converts to about 5.68 L/min or 0.341 m³/h.
Fire hydrant flow test
227.1 m³/h
A hydrant flow test reading of 1,000 GPM converts to 227.1 m³/h or 2.23 cfs — figures fire departments and engineers compare against NFPA flow requirements.
Which flow rate unit should I use?
GPM (US) is standard for US residential and commercial plumbing — hose bibs, showerheads, faucets, pump and water heater ratings. Imperial GPM shows up on older UK and Canadian fixtures and some pump curves. L/min and L/s are the metric standard used almost everywhere outside the US, and on international equipment spec sheets. m³/h is common for pumps, HVAC and industrial water systems in metric countries. CFM and cfs (cubic feet per minute/second) turn up in HVAC airflow contexts and in US civil and irrigation engineering for larger flows like stream or culvert discharge.
If you're comparing a US-rated fixture or pump to a metric spec sheet, convert both to the same unit before comparing — a "10 GPM" pump and a "40 L/min" pump are close but not identical (10 US GPM is 37.85 L/min).
Frequently asked questions
What does GPM mean?
GPM stands for gallons per minute, a measure of flow rate — the volume of water moving past a point each minute. Unless stated otherwise, GPM means US gallons per minute; imperial (UK) GPM is a separate, larger unit.
How do I convert GPM to L/min?
Multiply GPM by 3.785411784 to get liters per minute, since 1 US gallon equals exactly 3.785411784 liters. For example, 10 GPM equals 37.85 L/min.
What is the difference between US GPM and imperial GPM?
A US gallon is smaller than an imperial (UK) gallon, so US GPM and imperial GPM are different units for the same physical flow. 1 US GPM equals about 0.833 imperial GPM, and 1 imperial GPM equals about 1.201 US GPM.
How do I convert GPM to cubic feet per minute (CFM)?
Multiply GPM by 0.13368 to get CFM, since 1 US gallon equals 0.13368 cubic feet. For example, 100 GPM equals about 13.37 CFM.
How many GPM is a typical garden hose or showerhead?
A garden hose typically flows 9 to 17 GPM depending on diameter and pressure. A WaterSense-labeled low-flow showerhead is capped at 2.0 GPM, while older showerheads may use 2.5 GPM or more.
How is GPM related to cubic meters per hour (m³/h)?
Multiply GPM by 0.227125 to get m³/h, since 1 US gallon equals 0.003785411784 cubic meters and there are 60 minutes in an hour. For example, 50 GPM equals about 11.36 m³/h — a common way pump and pool equipment specs are compared internationally.
Sources & references
- National Institute of Standards and Technology (NIST). Guide for the Use of the International System of Units (SI) — exact volume and time unit definitions.
- International Bureau of Weights and Measures (BIPM). The International System of Units (SI).
John Mac, PE
Water Systems Specialist · Austin, Texas
Texas-licensed Professional Engineer with 13+ years in residential water systems and 180+ completed projects. Writes and reviews the calculators on watercalculator.us. Read full bio
Texas PE (2016) · BS Civil Engineering, Hydraulics (2013)