Flow Rate Unit Converter
Enter a flow in any one unit — US GPM, L/min, m³/h, or CFM — and read the equivalent in all four at once.
Equivalent flow rates
All conversions route through cubic metres per hour. US (imperial) gallons are used, not UK gallons — 1 US gpm ≈ 0.2271 m³/h. CFM is a volumetric rate at whatever the gas is actually at, not a standardized (SCFM) rate.
Keeping units straight
Flow data arrives in whatever unit its source happens to use. A pump curve might be in US GPM, a valve Kv in m³/h, a compressor rating in CFM, and a process spec in L/min. Before any sizing calculation, those all have to land in the same unit, and a mismatch here is one of the easiest ways to end up an order of magnitude off.
The one place to stay careful is gas. Volumetric flow for a compressible gas is only meaningful at a stated pressure and temperature, so “CFM” at the inlet of a valve is not the same physical amount of gas as CFM at the outlet. For incompressible liquids, a volumetric conversion is exact and unambiguous.
Frequently Asked Questions
Which units does this converter handle?
Four common volumetric flow units: US gallons per minute (GPM), litres per minute (L/min), cubic metres per hour (m³/h), and cubic feet per minute (CFM). Enter a value in any one and it shows the equivalent in all four, routing every conversion through cubic metres per hour as a common base.
Are these US gallons or UK gallons?
US (liquid) gallons. One US gallon is about 3.785 litres, so 1 US GPM ≈ 0.2271 m³/h ≈ 3.785 L/min. An imperial (UK) gallon is larger — about 4.546 litres — so an imperial GPM is roughly 20% more flow. Data sheets from US suppliers almost always mean US gallons.
How do GPM and m³/h relate?
1 US GPM equals 0.2271 m³/h, and 1 m³/h equals about 4.403 US GPM. For litres: 1 m³/h is 16.667 L/min, since a cubic metre is 1000 litres spread over 60 minutes. These are the conversions most valve and pump data sheets need.
Is CFM the same as SCFM?
No. CFM here is an actual volumetric rate — cubic feet per minute at the gas's actual pressure and temperature. SCFM (standard CFM) references a fixed standard condition and only equals actual CFM at that standard state. Because gas volume changes with pressure and temperature, converting CFM for a compressible gas needs those conditions; the volumetric conversion here treats it purely geometrically.
Can I use this for both liquids and gases?
The conversions are purely volumetric, so they are exact for any fluid as a unit conversion. For gases, remember that a volumetric flow only means something at a stated pressure and temperature — a valve passing a set mass of gas shows very different CFM at the inlet and outlet. For liquids, volumetric flow is effectively unaffected by modest pressure changes.
Engineering estimates for preliminary sizing — not professional engineering advice; verify with the valve manufacturer’s data and a qualified engineer before finalizing a selection.