What this calculator does
Endurance is how long an aircraft can keep flying on the fuel it is carrying; range is how far it can travel in that time. Both start from the same two numbers, usable fuel and the rate that fuel is burned, with range adding in the aircraft’s cruise speed to convert time into distance.
This is a still-air calculation: it assumes no wind at all. A headwind reduces the actual distance covered for the same endurance, a tailwind increases it, and real flight planning also builds in fuel reserves rather than treating every drop of usable fuel as available for the trip itself.
The formula
Divide usable fuel by the fuel burn rate to get endurance in hours. Multiply endurance by cruise speed to get still-air range, in whichever distance unit matches the speed unit entered.
| Term | Meaning |
|---|---|
| Usable fuel | The fuel actually available for the flight, excluding unusable fuel that cannot be drawn from the tanks. |
| Fuel burn rate | How much fuel the engine or engines consume per hour at the planned cruise power setting. |
| Endurance | Usable fuel divided by burn rate: how long the aircraft can fly before running out. |
| Range | Endurance multiplied by cruise speed: how far the aircraft can travel in still air on that fuel. |
The inputs explained
| Field | What to enter |
|---|---|
| Usable fuel on board (L) | The usable fuel on board for this flight, not including any unusable residual fuel. |
| Fuel burn rate (L/hr) | The expected fuel burn rate at your planned cruise power setting. |
| Cruise speed (knots) | Cruise speed in knots for a range in nautical miles, or in km/h for a range in kilometres. |
When to use it
Planning fuel for a cross-country flight
Comparing the calculated range against the planned trip distance, with a margin held back for reserves, is a basic check before any longer flight.
Deciding on a fuel stop
If the direct range without reserves falls short of the destination distance, this shows how much of a shortfall needs to be covered by a fuel stop en route.
Comparing power settings
A higher cruise power setting burns more fuel per hour but flies faster; comparing endurance and range at two power settings shows the actual trade-off for a specific trip length.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How endurance and range change with usable fuel, at a fixed burn rate and cruise speed
A fixed burn rate and cruise speed, across a range of usable fuel loads.
| Usable fuel | Endurance | Still-air range |
|---|---|---|
| 80 L | 2 h 17 min | 251 nm (or km, matching the speed unit entered) |
| 120 L | 3 h 25 min | 377 nm (or km, matching the speed unit entered) |
| 150 L | 4 h 17 min | 471 nm (or km, matching the speed unit entered) |
| 180 L | 5 h 8 min | 566 nm (or km, matching the speed unit entered) |
| 220 L | 6 h 17 min | 691 nm (or km, matching the speed unit entered) |
| 260 L | 7 h 25 min | 817 nm (or km, matching the speed unit entered) |
How range changes with fuel burn rate, at a fixed fuel load and cruise speed
A fixed fuel load and cruise speed, across a range of burn rates.
| Fuel burn rate | Endurance | Still-air range |
|---|---|---|
| 25 L/hr | 6 h 0 min | 660 nm (or km, matching the speed unit entered) |
| 30 L/hr | 5 h 0 min | 550 nm (or km, matching the speed unit entered) |
| 35 L/hr | 4 h 17 min | 471 nm (or km, matching the speed unit entered) |
| 40 L/hr | 3 h 45 min | 413 nm (or km, matching the speed unit entered) |
| 45 L/hr | 3 h 20 min | 367 nm (or km, matching the speed unit entered) |
| 50 L/hr | 3 h 0 min | 330 nm (or km, matching the speed unit entered) |
Questions
Why does this not build in a fuel reserve automatically?
Reserve requirements vary by regulation, aircraft type and flight rules (day VFR, night, IFR), so it is left for you to subtract from usable fuel before entering it, or to compare against the endurance figure shown here.
How does wind affect this calculation?
It does not account for wind at all: this is a still-air range. A headwind reduces the actual ground distance covered for the same endurance, and a tailwind increases it; combine this with the crosswind and headwind component calculator to see the effect of a specific wind.
Should I use best-economy or best-power cruise settings?
Whichever setting matches the fuel burn rate and cruise speed you enter; the calculator itself is neutral on which power setting to plan around, since that is an aircraft-specific and mission-specific choice.
What counts as usable fuel?
Total fuel on board minus any unusable fuel that cannot be drawn from the tanks in all flight attitudes, a figure specified in the aircraft’s flight manual rather than something the pilot chooses.
To account for wind on that same route, see the crosswind and headwind component calculator. For the true airspeed behind your cruise speed figure, see the true airspeed estimate calculator.