Conversion from Milliliters per second to US Gallons per second

Information about the Milliliter per second (mL/s)

The millilitre per second is a unit of volumetric flow rate equal to one millilitre of fluid passing a point every second. Its symbol is mL/s. Since a millilitre is a cubic centimetre, the unit is identical to the cubic centimetre per second, and the two names are used interchangeably depending on whether the fluid is thought of as a liquid or as a volume of space.

Volumetric flow rate is a volume divided by a time, so it has the dimensions of length cubed per second. That makes it convertible to any other flow unit by a single multiplication, and it also means that a flow rate multiplied by a duration gives the total volume delivered — the arithmetic that underlies every dosing calculation and every water bill.

A millilitre per second is a small but visible flow. A tap dripping steadily produces perhaps a tenth of this; a thin stream from a partly opened tap is a few millilitres per second; a garden hose at full flow is several hundred. In household terms it is the rate at which a teaspoon fills in about five seconds.

The unit belongs to the laboratory and to small machinery. Peristaltic pumps, dosing systems, fuel injectors and analytical instruments all work in this range, and their specifications are written in millilitres per second when the process is fast and in millilitres per minute when it is slow. Where a pump must deliver a precise quantity, the rate and the running time together define the dose.

Human physiology gives useful comparisons. Resting cardiac output is about eighty millilitres per second, urine production averages under a fiftieth of that, and saliva production is around a hundredth. The flow through a single capillary is far smaller still and is measured in cubic millimetres per hour.

Converting to the SI base unit requires care with the powers of ten. One millilitre per second is a millionth of a cubic metre per second, because a millilitre is a millionth of a cubic metre. That factor of a million between the practical unit and the base unit is why flow rates are almost never quoted in cubic metres per second outside hydrology and heavy engineering.

One millilitre per second equals 0.001 litres per second, 60 millilitres per minute, or about 0.0000353 cubic feet per second.

Information about the US Gallon per second (gal US/s)

The US gallon per second is a unit of volumetric flow rate equal to one United States gallon passing a point every second. Its symbol is gal US/s. The US gallon is exactly 3.785411784 litres, descended from the English wine gallon of 231 cubic inches, so one US gallon per second is a little under four litres every second.

Fire protection in the United States works at this scale. A fire hydrant flows several gallons per second, a pumper truck delivers 20 or more, and a large sprinkler system's design demand runs to tens. Fire codes state these figures in gallons per minute, but hydraulic calculations of friction loss in the mains use the per-second value, and the two are the same number divided by sixty.

Municipal water and wastewater engineering also reaches it. A neighbourhood water main carries a few gallons per second at peak hour, a lift station handles tens, and a treatment plant's influent hundreds. American practice usually states plant capacity in million gallons per day, and one gallon per second is 0.0864 million gallons per day — a conversion any water engineer performs from memory.

Industrial cooling and process water are described here as well. Condenser cooling water, quench flows and washdown systems all reach gallons per second, and the pump power required follows from the flow multiplied by the head, so an increase in flow of ten per cent shows up directly on the electricity bill.

The difference from the imperial gallon deserves a clear statement. The US gallon is about 17 per cent smaller than the imperial one, so the same numerical rate is a materially different flow on either side of the Atlantic. Equipment documentation should say which gallon it means, and prudent engineers convert to litres before comparing anything.

For scale, one US gallon per second is about 3.79 litres per second, and 0.264 US gallons per second is one litre per second. A flow of ten US gallons per second is nearly 38 litres per second, enough to fill a domestic bath in three seconds and comparable to a small stream.

One US gallon per second equals about 3.785 litres per second, about 0.003785 cubic metres per second, or about 0.8327 imperial gallons per second.