Breguet Range Equation

Engineering & Applied Technologies Dictionary
An analytical relation estimating cruise range R for a jet‑propelled aircraft under steady cruise by R = (V/c)·(L/D)·ln(Wi/Wf), where V is cruise speed, c is propulsion specific fuel consumption (fuel weight flow per unit thrust or power depending on formulation), L/D is lift‑to‑drag ratio, and Wi/Wf is initial-to‑final weight ratio.