Flow Rate Converter
Same value in every unit
| Unit | Value |
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Which gallon, and which fluid
Two things make flow rate figures go wrong. The first is the gallon: the UK gallon is 4.546 litres and the US gallon 3.785, so the same "10 GPM" rating means two noticeably different pumps. The second is assuming a rating meant for air applies to water, or the reverse — CFM is an air unit, L/min and m³/h are usually liquid.
The conversions that come up most
- 1 m³/h = 16.67 L/min
- 1 US GPM = 3.785 L/min
- 1 UK GPM = 4.546 L/min
- 1 CFM = 28.32 L/min
- 1 L/s = 60 L/min = 3.6 m³/h
Flow alone does not size equipment
A pump is defined by a curve, not a number: as the head it must overcome rises, the flow it can deliver falls. A pump rated "60 L/min" delivers that at some particular head and less at any greater one. The same applies to fans, where CFM falls as static pressure rises. Convert the units here, then read the manufacturer's curve for the duty you actually have.
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Frequently Asked Questions
No, and the gap is large — a UK gallon is 4.546 litres against the US 3.785, about 20% bigger. A pump rated at 10 GPM moves noticeably different amounts depending on which gallon the rating meant. Both are listed separately here.
Cubic feet per minute is the standard for air — fans, extractors, compressors and ventilation. Water and other liquids are normally quoted in litres per minute or cubic metres per hour, so seeing CFM usually tells you air is involved.
Flow rate is only half of it. A pump is specified by flow and by head — the height and resistance it must push against — and the two trade off against each other along the pump's curve. This converter handles the flow figure; the head has to come from the installation.
Because it produces convenient numbers for building services and industrial equipment. One cubic metre per hour is 16.67 litres per minute, which is a sensible domestic tap-sized flow.
Divide the volume by the flow rate in matching units. A 1,000 litre tank at 20 L/min takes 50 minutes, assuming the flow stays constant, which in practice it does not as the head changes.
No, the arithmetic runs in your browser.