Conversion from 2 Gallons per second to Milliliters per minute

Information about the Gallon per second (gal/s)

The gallon per second is a unit of volumetric flow rate equal to one imperial gallon passing a point every second. Its symbol is gal/s. The imperial gallon is 4.54609 litres, defined in 1824 as the volume of ten pounds of water at a stated temperature, so one gallon per second moves about four and a half litres — and, conveniently, about ten pounds — every second.

Firefighting is the discipline that works at this scale. A hose reel delivers a fraction of a gallon per second, a standard hose line 1 to 2, and a major pumping appliance 10 or more. British fire service practice quoted pump capacities in gallons per minute for most of the twentieth century, and the per-second figure is what a hydraulic calculation of pressure loss in the hose actually uses.

Large pumps and water mains reach it easily. A borehole pump on a farm might deliver half a gallon per second, a district water main several tens, and a river intake for a power station hundreds. Since the gallon of water weighs ten pounds, a flow in gallons per second converts to a mass flow in stones per second by dividing by 1.4, an arithmetic that older British engineering handbooks used freely.

Flood and drainage engineering in Britain used the unit until metrication. Culvert capacities, pumping station ratings and land drainage schemes were designed in gallons per second or per minute, and much of the surviving infrastructure still carries plates giving its capacity in those terms, which anyone assessing an old asset must convert with care.

The imperial gallon must be distinguished from the American one, which is 3.78541 litres — about twenty per cent smaller. A pump rated 10 gallons per second delivers 45.5 litres per second in Britain and 37.9 in the United States, a difference far too large to ignore in any calculation of capacity or of cost.

For scale, one gallon per second fills a domestic bath in about twenty-five seconds, and 0.22 gallons per second is one litre per second. A flow of ten gallons per second is a small stream, running at about 45 litres per second.

One gallon per second equals about 4.546 litres per second, about 0.004546 cubic metres per second, or about 1.201 US gallons per second.

Information about the Milliliter per minute (mL/min)

The millilitre per minute is a unit of volumetric flow rate equal to one millilitre passing a point every minute. Its symbol is mL/min. It is the working unit of clinical medicine and of analytical chemistry, two fields in which the quantity delivered matters far more than the speed of delivery.

Intravenous infusion is the clearest case. A drip is set in millilitres per hour for slow fluids and in millilitres per minute for fast ones, and an infusion pump is programmed with a rate and a volume. A litre of saline given over four hours runs at about four millilitres per minute; the same litre given rapidly in an emergency may run at a hundred.

Liquid chromatography works in the same range. A conventional analytical column is run at one millilitre per minute, a figure so standard that it appears as a default in almost every published method. Narrower columns run proportionally slower, and the flow must be held steady to within a fraction of a per cent, because the time at which a compound emerges depends on it.

Anaesthetic and oxygen delivery use the unit too, though there the fluid is a gas. Oxygen therapy is prescribed in litres per minute, and the small adjustments within that are made in hundreds of millilitres per minute. In each case the rate is a prescription, and the equipment exists to hold it constant.

Sixty millilitres per minute is one millilitre per second, so the conversion between the two is the same factor as between minutes and seconds. That relationship makes it easy to move between the fast and slow ends of the same equipment: a pump specified in millilitres per minute can be reasoned about in millilitres per second by dividing by sixty.

For everyday scale, a millilitre per minute would fill a teaspoon in five minutes and a cup in four hours. It is a rate slow enough that watching it is uninformative, which is why the instruments that use it display a totalised volume as well as a rate.

One millilitre per minute equals about 0.01667 millilitres per second, 60 millilitres per hour, or 0.001 litres per minute.