| Cubic metre per second | |
| Standard: | SI |
| Quantity: | volumetric flow rate |
| Symbol: | m3/s |
| Dimension: | L3·T−1 |
| Extralabel: | In SI base units |
| Extradata: | m3·s−1 |
A cubic metre per second (m3s−1, m3/s, cumecs or cubic meter per second in American English) is the unit of volumetric flow rate in the International System of Units (SI) equal to that of a stere or cube with sides of 1spell=inNaNspell=in in length exchanged or moving each second. It is popularly used for water flow, especially in rivers and streams, and fractions for HVAC values measuring air flow.
The term cumec is also used, as shorthand for "Cubic metres per second", with the plural form cumecs also common in speech. It is commonly used between workers in the measurement of water flow through natural streams and civil works, but rarely used in writing. Data in units of cumec are used along the y-axis or vertical axis of a flow hydrograph, which describes the time variation of discharge of a river (the mean velocity multiplied by cross-sectional area). A moderately sized river discharges in the order of 100 cumecs.
| 1 cubic metre per second | = | litres per second | ||
| = | kilolitres per minute | |||
| = | megalitres per day | |||
| = | gigalitres per year | |||
| ≈ | imperial gallons per second | |||
| ≈ | US gallons per second | |||
| ≈ | cubic feet per second | |||
| ≈ | cubic yards per second | |||
| ≈ | acre-feet per year | |||
| ≈ | cubic feet per year | |||
| ≈ | cubic miles per year |