A cubic foot per second (also cfs, cu ft/s, cusec and ft³/s) is an Imperial unit / U.S. customary unitvolumetric flow rate, which is equivalent to a volume of 1 cubicfoot flowing every second. Current official usage is largely confined to the United States and Canada, but like many imperial units which have officially been "abolished" in the United Kingdom, it remains familiar in that country, with extensive unofficial usage. It is popularly used for pipeline transport rates, water flow in rivers, and for HVAC measurements of air flow.
Symbols
There is no universally agreed symbol but the following are used: