| Cubic meters per minute (m³/min) | Cubic feet per second (ft³/s) |
|---|---|
| 1 Cubic meter per minute | 0.588577778733 ft³/s |
| 2 Cubic meters per minute | 1.17715555747 ft³/s |
| 3 Cubic meters per minute | 1.7657333362 ft³/s |
| 4 Cubic meters per minute | 2.35431111493 ft³/s |
| 5 Cubic meters per minute | 2.94288889367 ft³/s |
| 10 Cubic meters per minute | 5.88577778733 ft³/s |
| 20 Cubic meters per minute | 11.7715555747 ft³/s |
| 25 Cubic meters per minute | 14.7144444683 ft³/s |
| 50 Cubic meters per minute | 29.4288889367 ft³/s |
| 100 Cubic meters per minute | 58.8577778733 ft³/s |
| Reference | Cubic meters per minute (m³/min) | Cubic feet per second (ft³/s) |
|---|---|---|
| A domestic shower | 0.009 m³/min | 0.0052972 ft³/s |
| A kitchen tap | 0.01 m³/min | 0.00588578 ft³/s |
| A garden hose | 0.015 m³/min | 0.00882867 ft³/s |
| The Amazon river | 12540000 m³/min | 7380765 ft³/s |
The cubic metre per minute is a unit of volumetric flow rate equal to one cubic metre passing a point every minute. Its symbol is m³/min. It occupies the middle ground of industrial air handling: large enough for a factory's compressed-air main, small enough that the number stays in two or three digits.
Compressors are its most familiar users. A workshop screw compressor delivers 1 to 10 cubic metres per minute of free air, a large industrial machine 50 or more, and the rating is always given as free air delivery — the volume measured at atmospheric conditions rather than at the compressed pressure, because that is what the tools downstream actually consume.
Sizing a compressed-air system is an exercise in adding these numbers. Each tool has a consumption figure: an impact wrench 0.6 cubic metres per minute, a spray gun 0.3, a sandblasting nozzle several. Total them, apply a duty factor because they do not all run at once, add a margin for leaks, and the result is the compressor the workshop needs.
Mine and tunnel ventilation is quoted the same way. Regulations set a minimum air quantity per person and per unit of diesel power underground, and a working face may require 20 to 50 cubic metres per minute. The main fan at the surface handles the sum of every face, which is why the unit spans four orders of magnitude within a single industry.
Blowers, dust extraction and pneumatic conveying complete the picture. A woodworking dust extractor is rated at 20 to 60 cubic metres per minute, a bag filter for a cement plant at thousands, and a pneumatic conveyor is designed around the air velocity in the pipe, which the flow and the pipe cross-section together determine.
The conversion to its neighbours is easy in both directions. Sixty cubic metres per minute is one cubic metre per second, and one cubic metre per minute is a thousand litres per minute. That last relation is why the same fan can appear in a European catalogue as 1,200 litres per second and in another as 72 cubic metres per minute.
One cubic metre per minute equals about 0.01667 cubic metres per second, 1,000 litres per minute, or about 35.31 cubic feet per minute.
The cubic foot per second is a unit of volumetric flow rate equal to one cubic foot passing a point every second. Its symbol is ft³/s, and in hydrology it has a name of its own: the cusec. One cusec is about 28.32 litres per second, roughly the flow of a vigorous garden hose or a small brook.
American river gauging is entirely built on it. The United States Geological Survey publishes stream flow in cubic feet per second at thousands of gauges, water rights in the western states are granted in cusecs, and the Colorado's allocations between states rest on figures first written in this unit a century ago. The Mississippi at its mouth averages about 600,000 cubic feet per second.
Irrigation districts inherited it from the same tradition. A miner's inch, an older western measure, is defined in most states as a fixed fraction of a cusec, and a canal headgate is set to deliver a farmer's entitlement in cubic feet per second for a stated number of hours. The product of the two is the acre-foot, the volume unit that follows naturally from the cusec.
An easy approximation makes the unit memorable: one cubic foot per second flowing for twenty-four hours delivers almost exactly two acre-feet — 1.983, to be precise. Irrigation engineers use the round figure daily, since it converts a rate into a seasonal water budget in a single step.
Flood hydrology is written in it too. A design storm on a small catchment might produce a few hundred cubic feet per second, a major river flood tens or hundreds of thousands, and culverts, bridges and levees in the United States are sized against a peak discharge expressed exactly this way.
Its metric counterpart is the cubic metre per second, which is 35.31 times larger. Hydrological literature moves constantly between the two, and the ratio is worth remembering: a hundred cusecs is a little under three cubic metres per second, and a thousand cubic metres per second is a large river in anyone's units.
One cubic foot per second equals about 28.32 litres per second, about 0.02832 cubic metres per second, or about 448.8 US gallons per minute.