Fuel Endurance Calculator
Knowing your fuel endurance is critical for safe flight planning. Endurance is the time you can fly on your available fuel at a given burn rate, and it sets the outer boundary for range, reserve, and alternate planning. This calculator divides your usable fuel quantity (gallons) by your planned fuel burn rate (gallons per hour) to give total endurance in decimal hours and in hours and minutes. You should always subtract your required FAA reserve (30 minutes for VFR day, 45 minutes for VFR night, or the IFR alternate requirement under 14 CFR 91.167) to determine your usable flight time. The fuel burn rate should come from your aircraft Pilot Operating Handbook (POH) performance tables for the planned altitude and power setting.
Fuel endurance formula
Endurance (hours) = Usable Fuel (gal) / Burn Rate (GPH)
Usable fuel is the total fuel on board minus unusable fuel as listed in the aircraft's POH. The burn rate is obtained from the cruise performance tables for the planned altitude, power setting, and temperature. Subtract the required FAA reserve to find usable flight time before landing.
FAA fuel reserve requirements
- VFR day (14 CFR 91.151): fuel to first intended landing plus 30 minutes at cruise power.
- VFR night (14 CFR 91.151): fuel to first intended landing plus 45 minutes at cruise power.
- IFR (14 CFR 91.167): fuel to destination, alternate airport (if required), and then 45 minutes at normal cruise speed.
- Always add a personal reserve beyond the regulatory minimum, particularly for unfamiliar routes.
Fuel endurance calculator: frequently asked questions
What is fuel endurance?
Fuel endurance is the total time an aircraft can remain airborne with the fuel on board, at a specified power setting and fuel burn rate. It differs from range, which is the distance that can be covered.
How is fuel endurance calculated?
Fuel Endurance = Usable Fuel (gallons) / Fuel Burn Rate (GPH). For example, 38 gallons of usable fuel at 8.5 GPH gives 4.47 hours (4 hours 28 minutes) of endurance.
What is usable fuel?
Usable fuel is the total fuel on board minus unusable fuel (fuel that cannot be fed to the engine due to aircraft attitude or design). Unusable fuel quantities are listed in the aircraft's POH.
Does the FAA require a fuel reserve?
Yes. Under 14 CFR 91.151, VFR day flights must carry enough fuel to fly to the first intended landing point plus 30 minutes at cruise power. Night VFR requires 45 minutes. IFR rules require additional alternate fuel under 14 CFR 91.167.
How does altitude affect fuel burn?
At higher altitudes, fuel burn in GPH typically decreases for normally-aspirated engines operating at the same percentage of power. Always use the specific altitude performance data from your aircraft's POH cruise tables for accurate planning.
Official sources
- 14 CFR 91.151 (VFR fuel requirements): ecfr.gov.
- FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25B): faa.gov.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.