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Cubic metre per second
Unit systemSI
Unit ofvolumetric flow rate
In SI base unitsm3·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 one metre (39.37 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",[1] with the plural form cumecs also common in speech.[citation needed] 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  1000  litres per second
60  kilolitres per minute
86.4  megalitres per day
31.5576  gigalitres per year
≈  219.969248  imperial gallons per second
≈  264.172051  US gallons per second
≈  35.314454  cubic feet per second
≈  1.305  cubic yards per second
≈  25566.497  acre-feet per year
≈  1113676621  cubic feet per year
≈  0.00757090916  cubic miles per year


  1. ^ "Units: C", The University of North Carolina at Chapel Hill, webpage: UNC-Rowlett. Archived on June 2, 2018.

See also