Fuel Burn Endurance Calculator
Endurance is how long an aircraft can stay aloft on its fuel, found by dividing usable fuel by the fuel burn rate at your planned power setting. A safe plan also holds back a reserve so you never land on empty. This calculator subtracts your reserve from usable fuel, divides by the burn rate, and returns both total endurance and the usable endurance to your reserve. The fuel quantities and burn rate must come from your aircraft documents, not an assumption.
Endurance formula
total endurance = usable fuel / burn rate
endurance to reserve = (usable fuel - reserve) / burn rate
Total endurance burns every usable gallon; endurance to reserve stops when only your reserve remains, which is the time you should plan to. Both are in hours when fuel is in gallons and burn is in gallons per hour.
Worked example
With 50 gallons usable, a 10 gallon per hour burn, and an 8 gallon reserve: total endurance = 50 / 10 = 5.00 hours. Endurance to reserve = (50 - 8) / 10 = 4.20 hours. Plan flights to the 4.20 hour figure so you land with the 8 gallon reserve untouched.
Fuel burn endurance: frequently asked questions
How is flight endurance calculated?
Endurance is the usable fuel divided by the fuel burn rate. With usable fuel in gallons and burn in gallons per hour, endurance comes out in hours. Subtracting a fuel reserve before dividing gives the time you can fly while still landing with your required reserve intact.
What reserve should I keep?
Federal aviation regulations set minimum fuel reserves: for day VFR flight in the US, enough to fly to the first point of intended landing plus 30 minutes at normal cruise; 45 minutes at night and under IFR. The exact requirement depends on the rule you fly under, so enter your planned reserve in gallons.
Where do I get usable fuel and burn rate?
Usable fuel is the quantity available to the engine, listed in your aircraft's documents and always less than total tank capacity. Fuel burn rate at your planned power setting comes from the Pilot Operating Handbook performance tables. Use those figures; this calculator does not assume them.
Does endurance equal range?
No. Endurance is time aloft; range is distance, which also depends on groundspeed and wind. To get range, multiply usable endurance by groundspeed. Headwinds reduce range without changing endurance, which is why both numbers matter for planning.
Official sources
- U.S. Federal Aviation Administration: Pilot's Handbook of Aeronautical Knowledge.
- U.S. Federal Aviation Administration: FAA regulations and handbooks. Fuel reserve minimums are set in the federal aviation regulations; use your aircraft's usable fuel and burn rate.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.