The laminar burning velocity, , is a property of the combustible mixture. It is defined as the speed of the flame front relative to the fluid on the unburnt side of the flame. The burning velocity relative to the burnt fluid will be higher by a factor equal to the expansion ratio, .

Physically, the laminar burning velocity depends on the fuel, the equivalence ratio, the temperature of the unburnt mixture (preheating) and on pressure. Depending on the configuration in the simulation, it may be possible sometimes to neglect preheat and pressure dependencies. However, for partially premixed combustion, it is very important to account for the dependency on equivalence ratio. Specifically, the flammability limits have to be obeyed.