How do I calculate fuel for a flight in FSX?

To calculate fuel for an FSX flight, add taxi, climb, cruise, descent, alternate and reserve fuel. For each phase, multiply expected time in hours by that aircraft’s total fuel flow, then add the results. Load the final quantity in FSX’s Fuel and Payload screen without exceeding maximum take-off weight.

How do I calculate FSX fuel manually?

The reliable method for both boxed FSX and FSX: Steam Edition is to calculate each flight phase separately rather than multiplying the entire distance by one fuel figure.

Fuel required = taxi + climb + cruise + descent/approach + alternate + reserve + extra fuel

1. Plan the route and flight profile. Record route distance, cruise altitude, expected groundspeed and time for each phase. Our guide to setting up a route and reading the FSX navigation log explains where to obtain the basic distance and time figures.
2. Find the aircraft’s fuel flow. Use its manual, reference material or cockpit fuel-flow gauges. On a multi-engine aircraft, confirm whether the displayed figure is per engine or total; add the individual engine flows when necessary.
3. Calculate fuel for each phase. Multiply the time in decimal hours by the applicable total fuel flow. If only distance is known, use time = distance ÷ groundspeed, then add separate allowances for taxi, climb and approach.
4. Add alternate and reserve fuel. Alternate fuel covers the flight from the destination to the alternate. Reserve fuel remains after that and should not be treated as extra trip fuel.
5. Check units and aircraft weight. Keep the entire calculation in pounds, kilograms, US gallons or litres until the end. Confirm that fuel plus payload does not exceed the aircraft’s maximum gross or take-off weight.

The mistake we see constantly is using indicated airspeed instead of expected groundspeed. A headwind increases flight time and fuel burn even though the indicated cruise speed remains unchanged.

Worked FSX fuel example

This fictional single-engine example shows the arithmetic; its fuel-flow figures do not represent a particular FSX aircraft.

The total is 24.6 US gallons. Loading about 26 gallons avoids pretending the estimates are exact, provided that quantity is within the tank and weight limits. No alternate fuel is included in this example.

How much reserve fuel should I add in FSX?

For an ordinary non-dispatch simulator flight, 30–45 minutes at normal cruise or holding fuel flow is a practical baseline, plus enough fuel to reach an alternate when one is planned.

If recreating a real-world operation, use the reserve, contingency and alternate requirements for that flight and operator. Airline planning treats these as separate quantities, while a casual FSX general-aviation flight may use a simpler time-based reserve. Do not assume that an arbitrary percentage meets a particular real-world rule.

Can the FSX Flight Planner calculate fuel automatically?

FSX’s built-in Flight Planner and navigation log provide a basic estimated time and fuel figure, but that estimate should be treated as a starting point rather than a precise dispatch calculation.

It may not reflect your actual winds, taxi time, mixture setting, routing changes, holding or an add-on aircraft’s custom fuel model. For Boeing 747-400 planning, our downloadable FSX jet fuel planning calculator provides a more suitable aircraft-focused method than a flat distance estimate.

How do I load the calculated fuel in FSX?

Load the calculated block fuel through FSX’s Fuel and Payload screen before departure, distributing it between tanks as required by the aircraft.

• Keep corresponding left and right tanks balanced unless the aircraft documentation specifies another loading sequence.
• Check the displayed total weight and centre of gravity after adding passengers, baggage and cargo.
• Use an add-on aircraft’s own loading manager when its documentation requires it; changing fuel in the standard FSX screen may be overwritten.
• Disable Unlimited fuel in the realism settings if you want fuel consumption to be simulated.
• After loading, verify the cockpit quantity gauges and set the fuel selectors, pumps and crossfeed controls correctly.

If converting quantities, use the aircraft documentation or the weight displayed by FSX. As a rough FSX cross-check, aviation petrol is commonly treated as about 6.0 lb per US gallon and jet fuel as about 6.7 lb per US gallon. Do not confuse US gallons with Imperial gallons.

Why does actual FSX fuel burn differ from the plan?

Most fuel-planning errors come from incorrect units, unrealistic flight times or using a per-engine fuel flow as though it covered the whole aircraft.

• Time was entered incorrectly: 1 hour 30 minutes is 1.5 hours, not 1.30 hours.
• Wind was ignored: calculate cruise time with groundspeed rather than indicated or true airspeed alone.
• The route became longer: vectors, holding, missed approaches and diversions all add fuel.
• Mixture remained full rich: piston aircraft can burn substantially more fuel at altitude when the mixture is not leaned correctly.
• Weight or altitude changed: jet fuel flow varies with aircraft weight, power setting, altitude and temperature.
• An add-on controls fuel separately: its loader or custom systems may override the standard FSX quantity.
• Simulation rate was increased: fuel burn follows simulated elapsed time, so accelerated flight consumes fuel faster per real-world minute.

If the engines stop while the gauges still show fuel, check tank selection, pumps and crossfeed before adding more fuel. That is usually a fuel-feed problem rather than a planning error.