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Volumetric Flow Rate Converter
Convert litres per minute, cubic metres per hour, gallons per minute and CFM.
A pump datasheet says 15 m³/h. The irrigation kit you are plumbing it into is rated in litres per minute. Before you can tell whether that pump is even close to what the system needs, the two numbers have to speak the same language.
The units you will actually run into
- Litres per minute (L/min) — the everyday unit for taps, showerheads and small pumps.
- Cubic metres per hour (m³/h) — standard for industrial pumps, water utilities and larger plumbing systems.
- US gallons per minute (GPM) — the default in American plumbing, irrigation and pool pump specifications.
- Cubic feet per minute (CFM) — used for air flow rather than liquid — HVAC systems, compressors and fans.
Flow rate conversion factors
| From | To L/min | To m³/h | To US GPM |
|---|---|---|---|
| 1 L/min | 1 | 0.06 | 0.264 |
| 1 m³/h | 16.67 | 1 | 4.403 |
| 1 US GPM | 3.785 | 0.227 | 1 |
Sizing a pump or a shower correctly
A standard kitchen tap flows somewhere around 6–8 L/min. A modern low-flow showerhead in Europe is often restricted to about 8–9 L/min, while the US federal limit for showerheads has been 2.5 US GPM (about 9.5 L/min) since the Energy Policy Act of 1992. Several states go further — California requires 1.8 US GPM. Undersize a pump against these figures and water pressure drops noticeably the moment two fixtures run at once; oversize it and you are paying for capacity, and energy, you never use.
Where flow rate sizing actually matters
- HVAC: airflow is sized in CFM based on room volume and how many times per hour the air needs to be fully replaced.
- Irrigation: drip and sprinkler systems are designed around a total L/min or GPM budget so the supply pipe and pump can keep up.
- Aquariums and ponds: filter and pump turnover rate is usually specified as litres or gallons per hour, a close cousin of flow rate.
- Industrial process water: cooling and process lines are specified in m³/h because the volumes involved are far larger than a domestic L/min figure.
Flow rate conversion questions
How do I convert litres per minute to cubic metres per hour?
Multiply by 0.06. A pump rated at 500 L/min is delivering 30 m³/h, the kind of figure you would see on an industrial or agricultural pump nameplate.
What is a normal shower flow rate?
Modern low-flow showerheads run around 8–9.5 L/min (roughly 2.0–2.5 US GPM), down from older fixtures that could exceed 15 L/min. Efficiency standards differ by country and, in the US, by state, so check the limit that applies where you are.
Why does HVAC use CFM instead of litres per minute?
Because CFM measures air flow, not liquid flow, and US HVAC engineering standards were built around cubic feet from the outset. The underlying idea, volume moved per unit time, is identical to a liquid flow rate; only the fluid and the unit differ.
How many litres per minute is one US gallon per minute?
About 3.785 L/min, since a US gallon is 3.785 litres. A pump rated at 10 US GPM is moving roughly 37.85 litres every minute.
Does flow rate tell me the pressure a pump can deliver?
No, they are related but separate figures. Flow rate is how much volume moves per unit time; pressure, or head, is how much force is pushing it. A pump datasheet needs to be read against both, usually shown together on a performance curve.
