Estimate the still-air cruise range and endurance of a jet aircraft with the Breguet range equation. Enter cruise speed, lift-to-drag ratio, thrust-specific fuel consumption, and the start and end cruise weights — the calculator returns range, endurance, the weight ratio, and the fuel burned. SI units throughout.
The Breguet range equation is the single most important relationship in cruise-performance and aircraft sizing. It links how far a jet can fly to just three things — how efficiently the wing produces lift (L/D), how efficiently the engine burns fuel (the thrust-specific fuel consumption c), and how much of the aircraft's weight is fuel (the weight ratio W₀/W₁). This calculator evaluates both the range and the endurance forms for a jet aircraft in steady cruise.
For a jet in steady, level cruise the range is:
R = (V / (g₀·c)) · (L/D) · ln(W₀ / W₁)
where V is the true airspeed, g₀ = 9.80665 m/s², c is the thrust-specific fuel consumption (TSFC, in 1/s for a jet), L/D is the lift-to-drag ratio, W₀ is the weight at the start of cruise, and W₁ the weight at the end. The endurance — the time the aircraft can stay aloft — drops the speed term:
E = (1 / (g₀·c)) · (L/D) · ln(W₀ / W₁)
So range and endurance differ only by the cruise speed V: R = V·E. Maximum range and maximum endurance occur at different flight conditions because of this.
Grouping the equation as R = [V·(L/D)/(g₀·c)] · ln(W₀/W₁) makes the design levers obvious. The bracketed term is a pure efficiency: range increases linearly with cruise speed, linearly with aerodynamic efficiency L/D, and inversely with fuel consumption c. The logarithm of the weight ratio captures the fuel fraction. Because the fuel term is a logarithm, doubling the fuel does not double the range — there are diminishing returns, which is why ultra-long-range aircraft are dominated by structural and aerodynamic efficiency rather than simply carrying more fuel.
Every term in the bracket rewards efficiency. A high lift-to-drag ratio means the wing makes the lift it needs while creating little drag, so less thrust — and less fuel — is required. A low TSFC means the engine extracts more useful thrust from each kilogram of fuel, which is why modern high-bypass turbofans transformed airline economics. Flying faster increases range for a jet (the speed term V is in the numerator), up to the point where rising transonic drag erodes L/D. The best cruise condition balances these, typically near the speed for maximum V·L/D.
The Breguet equation is derived assuming L/D, V, and c stay constant through the cruise. As fuel burns and the aircraft gets lighter, holding L/D and speed constant requires the air density to fall — which means the aircraft must slowly climb. This idealised "cruise-climb" profile is the most fuel-efficient way to fly, and the equation is exact for it. Real flights fly stepped constant-altitude cruise for air-traffic reasons, so they fall slightly short of the Breguet ideal, but the equation remains the standard first-order estimate for range and sizing.
TSFC is the rate of fuel weight burned per unit of thrust produced. For a jet it has units of 1/s when fuel and thrust are both expressed as forces (weight flow per newton of thrust). A modern high-bypass turbofan in cruise has a TSFC of roughly 1.5–2×10⁻⁴ 1/s. Lower TSFC means a more efficient engine and, directly, longer range.
Propeller and jet engines are characterized differently. A jet burns fuel proportional to thrust, giving the V·(L/D)/c form shown here. A propeller burns fuel proportional to power, so its Breguet range uses propeller efficiency and a power-specific fuel consumption, and the speed term drops out — propeller range depends on L/D and not directly on V. This calculator implements the jet form.
As the aircraft burns fuel it gets lighter, so the thrust and fuel flow needed to cruise both decrease continuously. Integrating that changing fuel flow over the flight produces a natural logarithm of the start-to-end weight ratio. The practical consequence is diminishing returns: each extra tonne of fuel adds less range than the last.
The calculator reports range in kilometres and converts to nautical miles using 1 km = 0.539957 nmi (1 nmi = 1852 m). Nautical miles are the standard distance unit in aviation because one nautical mile equals one minute of latitude, which simplifies navigation.
No. The Breguet equation gives still-air (no-wind) range during the cruise phase only. Real mission range is reduced by climb and descent fuel, headwinds, reserves, and air-traffic routing, and increased by tailwinds. Treat the Breguet result as the ideal cruise range and apply mission allowances on top.