Fuel Endurance Calculator
Aircraft fuel endurance to your reserve and to dry tanks, plus range in still air and in wind, from fuel and fuel flow in gal, L, kg or lb and cruise speed. How it works
Use the Fuel Endurance Calculator
About the Fuel Endurance Calculator
50 gallons on board with an 8 gallon reserve, burning 8.5 GPH at 120 knots, gives 04:56 of endurance to reserve and 593 NM of range in still air. The fuel endurance calculator divides the fuel above the reserve by the fuel flow, then multiplies by ground speed. Burning the reserve too would stretch that to 05:53 and 706 NM, which is not a figure to plan on.
Endurance and range by fuel on board
| Fuel on board | Endurance to reserve | Range to reserve | Endurance to dry tanks |
|---|---|---|---|
| 20 gal | 01:25 (1.41 h) | 169 NM | 02:21 (2.35 h) |
| 30 gal | 02:35 (2.59 h) | 311 NM | 03:32 (3.53 h) |
| 40 gal | 03:46 (3.76 h) | 452 NM | 04:42 (4.71 h) |
| 50 gal | 04:56 (4.94 h) | 593 NM | 05:53 (5.88 h) |
| 60 gal | 06:07 (6.12 h) | 734 NM | 07:04 (7.06 h) |
| 80 gal | 08:28 (8.47 h) | 1016 NM | 09:25 (9.41 h) |
8 gal reserve, 8.5 GPH, 120 kt, still air. Range to reserve is endurance to reserve times cruise speed. The two endurance columns always differ by the time the reserve lasts, 00:56 at 8.5 GPH.
What the wind does to 50 gal, 8 gal reserve, 8.5 GPH, 120 kt
| Wind | Headwind component | Ground speed | Range to reserve |
|---|---|---|---|
| Calm | 0.0 kt | 120.0 kt | 593 NM |
| 10 kt headwind (from 0°) | 10.0 kt | 110.0 kt | 544 NM |
| 20 kt headwind (from 0°) | 20.0 kt | 100.0 kt | 494 NM |
| 30 kt headwind (from 0°) | 30.0 kt | 90.0 kt | 445 NM |
| 20 kt wind from 45° | 14.1 kt | 105.9 kt | 523 NM |
| 20 kt crosswind (from 90°) | 0.0 kt | 120.0 kt | 593 NM |
| 20 kt wind from 135° | -14.1 kt | 134.1 kt | 663 NM |
| 10 kt tailwind (from 180°) | -10.0 kt | 130.0 kt | 642 NM |
| 20 kt tailwind (from 180°) | -20.0 kt | 140.0 kt | 692 NM |
The wind direction is the direction the wind blows from, relative to your course: 0° is a direct headwind, 180° a direct tailwind and 90° or 270° a pure crosswind. A negative headwind component is a tailwind. Endurance does not change with wind, only the distance flown.
How to use this tool
- Pick the fuel unit (US gallons, litres, kilograms or pounds) and, for kg or lb, the fuel type. Enter the total fuel on board, the fuel flow per hour and the cruise speed in knots.
- Enter the reserve you want to land with, in the same unit (0 if none), then the wind speed in knots and the wind direction relative to your course: the reported wind direction minus your course, plus 360 if the result is negative.
- Read endurance to reserve as hours and minutes, the range in nautical miles in still air and with the wind, how long the reserve lasts, and the dry-tank figure for comparison.
Frequently asked questions
- How do I calculate fuel endurance?
- Subtract the reserve from the fuel on board and divide by the fuel flow: (50 − 8) ÷ 8.5 = 4.94 hours, shown as 04:56. Multiply by ground speed for range: 4.94 × 120 knots is 593 NM. The tool rounds the time to the nearest minute.
- How much does a headwind cut my range?
- Endurance stays at 04:56, but ground speed falls and the distance with it. With the default fuel, a 10 knot headwind gives 110 knots over the ground and 544 NM, a 20 knot headwind 100 knots and 494 NM, and 30 knots 90 knots and 445 NM. A 20 knot tailwind gives 140 knots and 692 NM.
- How much reserve fuel should I carry?
- For VFR flight in airplanes, 14 CFR 91.151 requires enough fuel to reach the first point of intended landing and then fly at least 30 minutes by day or 45 minutes at night at normal cruise speed. At 8.5 GPH that is 4.25 gallons or 6.375 gallons, which the tool shows as a reserve of 00:30 or 00:45. This is not flight-planning advice: your aircraft handbook and the rules that apply to your flight come first.
- How does the wind direction work in this tool?
- The direction is where the wind blows from, relative to your course: 0° is a direct headwind (wind from straight ahead), 180° a direct tailwind and 90° or 270° a pure crosswind. A 20 knot wind from 45° has a 14.1 knot headwind component, a ground speed of 105.9 knots and a range of 523 NM; from 135° the same wind is a 14.1 knot tailwind component, a ground speed of 134.1 knots and a range of 663 NM. A pure crosswind changes nothing here, because the tool does not model drift or the heading correction for it. A forecast or METAR gives the wind as a compass direction, so subtract your course first: flying a course of 300° with the wind from 270° at 15 knots, 270 − 300 = −30, plus 360 is 330°. Enter 330 and the tool shows a 13.0 knot headwind, 107.0 knots over the ground and 529 NM.
- Does it work in liters, pounds or kilometers?
- Litres, kilograms and pounds yes; kilometers no. Pick the fuel unit and the fuel flow and reserve follow it. 190 L on board, 32 L per hour and a 30 L reserve give 05:00 to reserve and 600 NM at 120 knots. For kg or lb pick Avgas 100LL (6.01 lb per US gallon) or Jet A (6.68), the FAA densities at 59 °F; real fuel is lighter when warm. Speeds stay in knots and range in nautical miles. The limits are 100,000 gallons of fuel, 10,000 knots, and an endurance of at most 100,000 hours (100,000 gallons is 378,541 L); a blank field shows a message and no result instead of being read as 0.
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