TSFC may also be thought of as fuel consumption (grams/second) per unit of thrust (kilonewtons, or kN). It is thus thrust-specific, meaning that the fuel consumption is divided by the thrust.
TSFC or SFC for [[reaction engine|thrust engine]]s (e.g. [[turbojet]]s, [[turbofan]]s, [[ramjet]]s, [[rocket engine]]s, etc.) is the mass of [[fuel]] needed to provide the net thrust for a given period e.g. lb/(h·lbf) (pounds of fuel per hour-pound of thrust) or g/(s·kN) (grams of fuel per second-kilonewton). Mass of fuel is used rather than volume (gallons or litres) for the fuel measure since it is independent of temperature.<ref>[http://selair.selkirk.bc.ca/Training/Aerodynamics/range_prop.htm Specific Fuel Consumption<!-- Bot generated title -->]</ref>
Specific fuel consumption of air-breathing jet engines at their maximum efficiency is more or less proportional to speed. The fuel consumption ''per mile'' or ''per kilometre'' is a more appropriate comparison for aircraft that travel at very different speeds. There also exists [[power specific fuel consumption]], which equals speed times the thrust specific fuel consumption. It can have units of pounds per hour per horsepower.