| Cubic centimeters per minute (cm³/min) | Gallons per second (gal/s) |
|---|---|
| 1 Cubic centimeter per minute | 0.00000366615413832 gal/s |
| 2 Cubic centimeters per minute | 0.00000733230827664 gal/s |
| 3 Cubic centimeters per minute | 0.000010998462415 gal/s |
| 4 Cubic centimeters per minute | 0.0000146646165533 gal/s |
| 5 Cubic centimeters per minute | 0.0000183307706916 gal/s |
| 10 Cubic centimeters per minute | 0.0000366615413832 gal/s |
| 20 Cubic centimeters per minute | 0.0000733230827664 gal/s |
| 25 Cubic centimeters per minute | 0.000091653853458 gal/s |
| 50 Cubic centimeters per minute | 0.000183307706916 gal/s |
| 100 Cubic centimeters per minute | 0.000366615413832 gal/s |
| Reference | Cubic centimeters per minute (cm³/min) | Gallons per second (gal/s) |
|---|---|---|
| A domestic shower | 9000 cm³/min | 0.0329954 gal/s |
| A kitchen tap | 10000 cm³/min | 0.0366615 gal/s |
| A garden hose | 15000 cm³/min | 0.0549923 gal/s |
| The Amazon river | 1.254 × 1013 cm³/min | 45973573 gal/s |
The cubic centimetre per minute is a unit of volumetric flow rate equal to one cubic centimetre passing a point every minute. Its symbol is cm³/min, and since a cubic centimetre is a millilitre, mL/min means the same thing. It is the standard unit of controlled gas flow in laboratories and in the semiconductor industry.
That industry gave it an abbreviation of its own: sccm, standard cubic centimetres per minute. The word standard matters, because a gas expands and contracts with temperature and pressure, so a volume flow means nothing until the conditions are pinned down. A mass flow controller set to 50 sccm delivers a fixed number of molecules per minute regardless of what the downstream pressure does, which is precisely what a deposition or etching process requires.
A silicon wafer passing through a plasma etcher meets several such controllers at once — argon at a few hundred sccm, a reactive fluorine compound at tens, oxygen at a handful — and the recipe that defines the process is essentially a list of these numbers against time. Repeating a process in another factory means reproducing the same flows.
Chromatography and gas analysis use the unit at the low end. Helium carrier gas through a capillary column runs at one or two cubic centimetres per minute, a flame detector burns hydrogen at thirty and air at three hundred, and a mass spectrometer's inlet is designed around a flow the vacuum pumps can cope with.
Liquids appear here as well, particularly in analytical chemistry and medicine. A high-performance liquid chromatography pump runs at 0.2 to 2 cubic centimetres per minute, and an intravenous infusion of 100 millilitres over an hour is 1.67 cubic centimetres per minute. In both cases the small, steady rate is what allows the result to be reproduced.
Sixty cubic centimetres per minute is one cubic centimetre per second, and a thousand is a litre per minute. So a typical mass flow controller set to 500 sccm is delivering half a litre of gas a minute — about the volume of a soft-drink bottle, which is a helpful way to picture what an invisible gas line is actually carrying.
One cubic centimetre per minute equals one millilitre per minute, about 0.01667 cubic centimetres per second, or 0.001 litres per minute.
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.