How to plan fuel for a VFR or IFR flight
Trip fuel is time multiplied by fuel flow. Time is distance divided by groundspeed (not true airspeed — use the E6B wind triangle or a GPS groundspeed). Then add taxi or run-up fuel, fuel to an alternate if you need one, and a reserve.
For airplanes in the United States, the reserve times in this planner follow the FARs:
- 14 CFR 91.151 (VFR) — enough to fly to the first point of intended landing, and thereafter for at least 30 minutes by day or 45 minutes at night, at normal cruising speed.
- 14 CFR 91.167 (IFR) — enough to fly to the intended destination, then to an alternate airport when one is required under 91.169, and thereafter for 45 minutes at normal cruising speed.
Those rules are the legal floor, not a complete dispatch standard. Many operators and personal minimums add more. Helicopter reserves are shorter; this page is built around airplane numbers.
Gallons and pounds (100LL and Jet-A)
US flight-planning practice is 6.0 lb per US gallon for 100LL and 6.7 lb per US gallon for Jet-A. The aviation unit converter also handles litres and kilograms if you are working from a metric fuel slip. When weight-and-balance has to be exact, use the density in the POH or a measured specific gravity, not the planning round number.
Worked example
180 nm at 120 kt, 10 gph, 100LL, VFR day, no taxi, no alternate:
- Time = 180 / 120 = 1.5 hours.
- Trip fuel = 1.5 × 10 = 15 gal (90 lb).
- VFR day reserve = 0.5 × 10 = 5 gal.
- Total required = 20 gal / 120 lb.
The same leg under IFR with a 60 nm alternate and 1.5 gal for taxi is 15 + 5 + 7.5 + 1.5 = 29 gal.
How to use it
- Enter distance and groundspeed, then the burn in gallons per hour, pounds per hour, or litres per hour.
- Choose 100LL, Jet-A, or a custom density, and a VFR day, VFR night, IFR, or custom reserve.
- Optionally add taxi fuel, an alternate, and usable fuel on board to see endurance and whether you have a surplus.
- Compare the total with the usable fuel in the tanks and with the weight and balance of the airplane.
Frequently asked questions
How much reserve fuel do I need for VFR and IFR?
For airplanes, 14 CFR 91.151 requires enough fuel to fly to the first point of intended landing and then for 30 minutes by day, or 45 minutes at night, at normal cruising speed. Under 91.167, IFR fuel must take you to the destination, then to an alternate if one is required, and then for 45 minutes at normal cruise. This page applies those times to the burn rate you enter; it does not decide whether an alternate is required.
How many pounds are in a gallon of 100LL or Jet-A?
The usual US flight-planning figures are 6.0 pounds per US gallon for 100LL (avgas) and 6.7 pounds per US gallon for Jet-A or Jet-A-1. Actual density changes with temperature, so use the figure in your POH or a measured density when the weight has to be exact.
How do I calculate endurance and range?
Endurance in hours is usable fuel divided by fuel flow. Range is endurance times groundspeed. This planner also subtracts taxi and the reserve you selected so you can see fuel remaining above a legal-style reserve.
Does this include an IFR alternate?
If you check “include an alternate” and enter an alternate distance, the planner adds fuel to fly that distance (at the same or a different groundspeed) on top of the 45-minute IFR reserve. Whether 91.169 actually requires an alternate for your flight is a separate legal question.