Fuel Reserve Calculator
Carrying the correct minimum fuel reserve is a legal requirement under 14 CFR Part 91, and exceeding the minimum with a personal reserve is a widely recommended safety practice. This calculator computes the FAA minimum reserve fuel in gallons and total fuel required for a planned flight. Select your flight type (VFR day, VFR night, or IFR), enter your cruise fuel burn rate (GPH), the estimated flight time to destination, and for IFR flights the estimated time to the alternate airport. The calculator returns the minimum reserve fuel, the trip fuel, and the total fuel required at departure. All outputs are in US gallons.
Fuel reserve formula
Trip Fuel = Burn Rate (GPH) x Trip Time (hours)
VFR Day Reserve = Burn Rate x 0.5 hours (30 min)
VFR Night Reserve = Burn Rate x 0.75 hours (45 min)
IFR Reserve = Burn Rate x (Alternate Time + 0.75 hours)
Total Required = Trip Fuel + Reserve Fuel
References: 14 CFR 91.151 (VFR fuel requirements) and 14 CFR 91.167 (IFR fuel requirements). These are the FAA regulatory minimums. Actual fuel on board must also account for taxi, takeoff, climb, and descent fuel variations from cruise values.
Practical fuel planning guidance
- Use the cruise burn rate from your POH at the planned altitude and power setting.
- Add a personal reserve of 30-60 minutes beyond the regulatory minimum for cross-country flights.
- Plan for fuel availability at your destination. Not all airports have fuel service at all hours.
- Watch the fuel gauges in flight. Never rely solely on time calculations if fuel quantity gauges show lower than expected.
Fuel reserve calculator: frequently asked questions
What is the FAA fuel reserve requirement for VFR flights?
Under 14 CFR 91.151, VFR day flights must carry enough fuel to fly to the first intended landing point plus at least 30 minutes at cruise power. VFR night flights require at least 45 minutes of additional fuel.
What fuel reserve is required for IFR flights?
Under 14 CFR 91.167, IFR flights must carry fuel to fly to the destination, then to the alternate airport (if required), and then for 45 more minutes at normal cruise speed. The alternate fuel is included in this calculation.
Is the FAA minimum reserve the same as a safe reserve?
The FAA minimums are legal minimums, not operational best practice. Many pilots and operators add a personal reserve of 30-60 minutes on top of the regulatory minimum, especially for cross-country flights or when weather uncertainty exists.
Does fuel reserve apply to fuel on board or fuel remaining at destination?
The requirement applies to fuel at the destination. You must plan to arrive at the destination with the reserve amount remaining, not just to carry it at departure. Factor in cruise fuel burn from departure to destination to determine total fuel needed at departure.
How do I calculate total fuel required for a VFR day flight?
Total fuel = (leg distance / ground speed) x burn rate + (30 minutes / 60) x burn rate. For example, a 120-nm leg at 100 knots with 8 GPH burn = 1.2 hours x 8 + 0.5 hours x 8 = 9.6 + 4 = 13.6 gallons total required.
Official sources
- 14 CFR 91.151 (Fuel requirements for VFR flight): ecfr.gov.
- 14 CFR 91.167 (Fuel requirements for IFR flight): ecfr.gov.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.