Flow rate converter

What it's for

Flow rate says how much water passes in a given time, and it's needed every time you choose a pump, size an irrigation system, judge a tap or work out how long a tub takes to fill. The practical problem is that every trade uses a different unit: pumps talk in cubic metres per hour, taps in litres per minute, American catalogues in gallons per minute.

The everyday numbers worth knowing

1 m³/h = 16.67 L/min, and that's the conversion needed most often, because the pump is sold by a catalogue and the tap is measured by a bucket. A kitchen tap typically gives 6-10 L/min, a shower head 8-12, a washing machine uses between 40 and 60 litres a cycle. A half-inch garden hose, at normal household pressure, sits around 12-15 L/min.

The simplest way to measure a real flow rate without instruments: a ten-litre bucket and a stopwatch. If it fills in a minute, that's 10 L/min; in thirty seconds, 20.

Flow and pressure are two different things

This is the mistake that gets the wrong pump bought. Pressure (measured in bar, or in metres of head) says how high or how far the water can get; flow says how much of it arrives. The two are linked: the higher the same pump has to push, the fewer litres per minute it gives, which is why in catalogues the flow isn't a single number but a curve. The value that counts is the one at the head you actually need, not the headline figure, which is measured at zero metres.

Nearby tools

For volume units there is Volume converter, for pressure Pressure converter and for durations Time converter. If the sum concerns household water use, the running cost of the heater and pump is estimated by Electricity cost.