Specific Range Calculator
Specific range is the fundamental fuel efficiency metric in aviation, representing the distance flown per unit of fuel burned. For piston aircraft it is typically expressed in nautical miles per US gallon; for turbine aircraft, nautical miles per pound of fuel. Maximizing specific range at a given weight requires flying at the speed and altitude where the ratio of lift to drag is highest, and where engine efficiency is optimized. This calculator computes specific range from ground speed and fuel flow, and also calculates total range from available fuel. It accepts both GPH (gallons per hour) and lb/hr inputs.
Specific range formula
Specific Range (nm/gal) = Ground Speed (knots) / Fuel Flow (GPH)
Specific Range (nm/lb) = Ground Speed (knots) / (Fuel Flow (GPH) x 6.0 lb/gal)
Total Range (nm) = Usable Fuel (gal) x Specific Range (nm/gal)
Avgas (100LL) weighs 6.0 lb per US gallon. Jet-A weighs approximately 6.7 lb per US gallon. The conversion factor shown here uses 6.0 lb/gal for avgas. For turbine aircraft using lb/hr fuel flow, divide GS by the lb/hr value directly to get nm/lb.
Optimizing specific range
- For piston aircraft, specific range is typically maximized at 65-75% power at a moderate altitude where the engine can run lean of peak.
- For turboprops, the best specific range speed is often close to the maximum range cruise speed in the POH.
- Headwinds reduce effective specific range over the ground; include the wind correction when comparing range options.
- As fuel burns off and the aircraft gets lighter, the optimum range speed decreases. Step-climbing or cruise-climb can maintain efficiency.
Specific range calculator: frequently asked questions
What is specific range?
Specific range is the distance flown per unit of fuel consumed. It is expressed as nautical miles per pound of fuel (nm/lb) or nautical miles per US gallon (nm/gal). It is the aviation equivalent of miles per gallon for automobiles.
How is specific range calculated?
Specific Range (nm/lb) = Ground Speed (knots) / Fuel Flow (lb/hr). If using gallons, Specific Range (nm/gal) = Ground Speed (knots) / Fuel Flow (gal/hr). A higher specific range means better fuel efficiency.
What affects specific range?
Specific range is maximized at the best-range airspeed where the ratio of lift to drag is maximized. It decreases at higher or lower airspeeds, at non-optimal altitudes, in headwinds, and at higher gross weights. Power management settings from the POH optimize specific range.
What is the difference between specific range and fuel endurance?
Fuel endurance measures how long you can fly (time) on available fuel. Specific range measures how far you can fly (distance) per unit of fuel. Maximum endurance speed (typically slower) and maximum range speed are different optimal speeds.
How does altitude affect specific range for jet aircraft?
For jet aircraft, specific range typically increases with altitude because drag decreases with thinner air at constant Mach, and jet engine specific fuel consumption improves at altitude. Most jets achieve best specific range at the optimum cruise altitude for the aircraft weight.
Official sources
- FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25B), Chapter 11: faa.gov.
- FAA Aviation Maintenance Technician Handbook Powerplant (FAA-H-8083-32): faa.gov.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.