Sky DutyFree Aviation Fuel Burn Calculator
Turn fuel flow and flight time into fuel used and fuel weight for Jet-A, avgas, or diesel, or run it in reverse to get endurance from the fuel on board. Fuel weights match the Sky Duty E6B. No download, no account.
Fuel planning basics
Fuel burn is the bridge between how long you fly and how much fuel — by volume and by weight — that costs you. The core relationship is simple: fuel used equals fuel flow times time. Run a cruise fuel flow in gallons per hour against your planned flight time and you get the gallons the trip needs. Turn the same relationship around and you get endurance: divide the usable fuel on board by the fuel flow to see how many hours you can stay airborne. This calculator does both directions and adds the fuel's weight, because weight is what the aircraft actually has to carry.
Jet fuel weight and fuel weight in weight and balance
Fuel is one of the heaviest variable loads on an aircraft, so its weight matters for takeoff performance and for weight and balance. Gallons become pounds by multiplying by the fuel's density. This tool uses the same constants as the Sky Duty E6B:
- Jet-A — 6.7 lb per US gallon, the standard figure for turbine and jet fuel.
- Avgas 100LL — 6.0 lb per US gallon, for piston aircraft.
- Diesel / Jet-A in a diesel — approximately 6.8 lb per US gallon.
These are standard-temperature figures; fuel is slightly denser when cold and less dense when hot, so treat them as planning values. To put the fuel weight into a loading calculation, take the pounds from here and enter them as a station in the weight and balance calculator.
Always plan reserves
Trip fuel is not the whole picture. Regulations require a fuel reserve on top of the fuel needed to reach your destination: under 14 CFR 91.151, day VFR requires enough to fly to the first point of intended landing plus 30 minutes at normal cruise and night VFR 45 minutes, while IFR fuel requirements (alternate plus 45 minutes) fall under 14 CFR 91.167. The endurance this calculator shows is total flying time to dry tanks, so subtract your required reserve to find the usable trip time. Fuel planning is one input among many — always cross-check against your aircraft's POH and current conditions.
Worked example
Plan a flight at a cruise fuel flow of 12 gallons per hour for 2.5 hours. Fuel used is 12 × 2.5 = 30 gallons. If the aircraft burns Jet-A at 6.7 lb per gallon, that fuel weighs 30 × 6.7 = 201 lb. Run it the other way for endurance: with 50 usable gallons at 12 gallons per hour, endurance is 50 ÷ 12 ≈ 4.17 hours, or about 4h 10m to dry tanks — from which you would subtract your reserve before committing to a leg.
The same tools, offline in the cockpit
This fuel math is part of the E6B built into the Sky Duty iOS app, alongside scheduling, logbook, maintenance, and expense tracking. All of it works offline, so you can run the numbers at a remote strip with no signal. Sky Duty is not an electronic flight bag; always confirm fuel planning against your aircraft POH and the regulations.
Frequently Asked Questions
How do you calculate fuel burn?
What does jet fuel weigh per gallon?
How much does avgas weigh per gallon?
How do I calculate flight endurance from fuel?
Do I need to add fuel reserves?
Get the full E6B in Sky Duty
Fuel burn, fuel weight, density altitude, and wind — plus scheduling, logbook, maintenance, and expenses. All in one offline-first iOS app.
