Aircraft Specific Range Calculator
Specific range is the aviation version of fuel economy: the distance an aircraft travels for each unit of fuel burned. It is simply ground speed divided by fuel flow, and its reciprocal, fuel per mile, lets you turn a leg distance straight into trip fuel. Cruise planning is largely about finding the altitude, speed, and power setting that maximise specific range at the current weight, because that is what stretches range and minimises cost. This calculator returns specific range, fuel per nautical mile, and the total still-air range available on a given fuel quantity. Use ground speed, not airspeed, so wind is accounted for.
Specific range formula
Specific range = ground speed / fuel flow
Fuel per nm = fuel flow / ground speed
Range on fuel = specific range * usable fuel
Endurance = usable fuel / fuel flow
Ground speed in knots over fuel flow per hour gives nautical miles per unit of fuel. Fuel per nautical mile is the reciprocal and multiplies directly by leg distance to give trip fuel.
Specific range in cruise planning
- Maximum specific range cruise stretches range and lowers fuel cost for a given weight.
- A tailwind raises specific range; a headwind lowers it, so always use ground speed.
- As fuel burns off, lower weight shifts the optimum altitude and speed upward.
- Range on fuel here is gross; subtract reserve fuel before treating it as usable range.
- Fuel per mile times leg distance gives trip fuel without computing time aloft first.
Specific range: frequently asked questions
What is specific range?
Specific range is the distance an aircraft travels per unit of fuel burned, the aviation equivalent of miles per gallon. It equals ground speed divided by fuel flow. Higher specific range means more efficient cruise, and pilots seek the altitude, speed, and power setting that maximises it for a given weight.
How do I calculate specific range?
Divide ground speed by fuel flow in consistent time units. If ground speed is in knots (nautical miles per hour) and fuel flow is in gallons per hour, the result is nautical miles per gallon. The hours cancel, leaving distance per unit of fuel.
Why use ground speed rather than airspeed?
Specific range measures distance made good over the ground per unit of fuel, so it must use ground speed. A tailwind raises ground speed without raising fuel flow, improving specific range; a headwind does the opposite. Using true airspeed would describe air distance per unit fuel, which is a different quantity.
What is fuel per nautical mile?
Fuel per nautical mile is the reciprocal of specific range, the fuel flow divided by ground speed. It tells you how much fuel each mile costs and is convenient for multiplying by leg distance to get trip fuel directly, without first finding the time aloft.
How does weight affect specific range?
A heavier aircraft must generate more lift, which increases induced drag and the thrust and fuel flow needed to hold a given speed, lowering specific range. As fuel burns off and weight falls, the best specific range altitude and speed change, which is why long flights step-climb to stay near optimum.
Official sources
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.