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Fuel Burn Calculator

Estimate how much fuel a flight leg will burn, plus your reserve.

How it is calculated

The tool multiplies the hourly burn rate by time. fuel used = burn rate × flight time (h), reserve fuel = burn rate × reserve time (h) and total = fuel used + reserve fuel. The reserve is entered as a number of hours, not a volume, so 0.75 means 45 minutes at the same burn rate. All three results are rounded to two decimals. Burn rate and flight time must be above zero. The reserve is optional: left blank it counts as 0, and a negative reserve gives no result. The unit selector (gallons, litres, kilograms) only labels your numbers. The arithmetic is identical, so the burn rate must be in the unit you choose. The tool applies no regulatory minimum and no allowance for taxi, climb, wind or alternates.

Worked example

An aircraft burns 9.5 gallons per hour on a 3.2-hour leg with a 0.75-hour reserve. Fuel used: 9.5 × 3.2 = 30.40. Reserve fuel: 9.5 × 0.75 = 7.125, shown as 7.13. Total: 30.40 + 7.125 = 37.525, shown as 37.53. The tool displays a total of 37.53, fuel used of 30.40 and reserve fuel of 7.13 gallons. Choosing litres with the same numbers gives the same figures.

Try this example →

Common mistakes

  • Entering the reserve as a volume, such as 7 gallons. The field is hours, so 7 means seven hours of reserve and the result is huge.
  • Entering minutes instead of hours. 45 minutes must be typed as 0.75, and a flight time of 3 h 12 min as 3.2.
  • Changing the unit selector to convert. It does not convert between gallons, litres and kilograms, it only changes the label, so enter the burn rate in the unit you select.
  • Using a cruise burn rate for the whole trip. Taxi, take-off and climb burn more than cruise, and the tool adds nothing for them.
  • Trying a negative reserve to take fuel off the total. A negative reserve is rejected and no result is shown; leave the field blank or enter 0 for no reserve.

About this calculator

Fuel burn planning starts with a fuel flow or burn rate — the gallons or pounds an engine consumes per hour at a given power setting — multiplied by planned flight time to get fuel required for the leg itself, then adds a reserve margin on top. The FAA requires VFR flights to carry at least 30 minutes of reserve fuel by day (45 minutes at night), while IFR flights must plan for 45 minutes of reserve at normal cruise, so reserve fuel isn’t optional padding but a regulatory minimum baked into every flight plan.

Pilots, flight instructors, and dispatchers calculate fuel burn during preflight planning to confirm an aircraft can complete a route with legal reserves intact, especially before cross-country flights, and to decide whether a fuel stop is needed. Owners of small aircraft also use burn-rate figures to compare the real-world efficiency of different cruise power settings against published performance charts.

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