How do I calculate fuel and refuel in a flight simulator?

Block fuel is the total fuel required at the departure stand, including taxi fuel—yes, taxi is included—plus trip fuel and planned reserves. Load block fuel as the final onboard quantity; if an interface asks for uplift, subtract fuel already aboard. This simulator-only guidance is not for real-world flight planning.

This is general civil flight-simulator guidance for Microsoft Flight Simulator, X-Plane, Prepar3D and FSX. The planning principles are shared, but menus, units and add-on fuel systems differ.

What is block fuel, and does block fuel include taxi fuel?

Block fuel is everything expected to be onboard before departure from the stand. Does block fuel include taxi fuel? Yes—oui, ja: taxi fuel is one of its components, not an amount added afterwards.

Block fuel = taxi + trip + contingency + alternate + final reserve + additional fuel

Trip fuel is not block fuel. Loading only the trip figure omits taxi and reserves. Expected take-off fuel is normally block fuel minus the fuel actually consumed before take-off.

Is block fuel the amount to load or the uplift?

Block fuel is normally the required final onboard quantity. Uplift is only the amount added during refuelling.

Required uplift = target block fuel − usable fuel already onboard

If the target is 750 kg and the aircraft already has 200 kg usable fuel, request a 550 kg uplift. Enter 750 kg only when the field asks for total or target fuel; entering 750 kg as the uplift would leave about 950 kg onboard.

Check whether the reported fuel remaining is usable or total fuel. An aircraft may retain fuel that cannot feed the engines, and some add-ons model that distinction.

How do I calculate how much fuel to load?

There is no universal answer to “how much fuel?” or “quanto carburante?” because the quantity depends on the exact aircraft, payload, route, altitude, wind and reserve policy.

1. Select the exact aircraft profile. Match the variant, engine and add-on rather than using a vaguely similar aircraft. Enter the intended payload and centre of gravity.
2. Calculate by flight phase. Add climb fuel, cruise time multiplied by cruise fuel flow, and descent or approach fuel. If the published flow is per engine, multiply it by the number of operating engines.
3. Account for wind and altitude. Use wind-adjusted groundspeed to obtain cruise time. The most economical altitude may also change with weight, temperature and route length.
4. Add taxi and reserves once. Include contingency, alternate, final reserve and known extra fuel, but do not add them again if the dispatch result already reports block fuel.
5. Check capacity and mass limits. The fuel must fit within usable tank capacity without exceeding ramp, take-off or landing mass limits.
6. Review landing fuel. Predicted fuel at the destination or alternate should leave the planned final reserve protected.

Our explanation of the phase-by-phase flight-time and fuel-burn calculation covers the underlying time, distance and fuel-flow formulas.

Simple block-fuel arithmetic

Suppose a fictional plan contains 50 kg taxi fuel, 420 kg trip fuel, 25 kg contingency, 90 kg alternate fuel, 120 kg final reserve and 45 kg additional fuel.

50 + 420 + 25 + 90 + 120 + 45 = 750 kg block fuel

The aircraft starts with 750 kg at the stand, not 420 kg. Expected take-off fuel is 700 kg after taxi. Predicted destination fuel is 280 kg if the trip uses exactly 420 kg. These figures demonstrate the arithmetic; they are not recommendations for any aircraft.

What is a fuel factor?

A fuel factor is a multiplier or percentage bias applied to planned fuel burn when the simulated aircraft consistently consumes more or less than its baseline profile predicts.

Observed fuel factor = actual consumption ÷ planned consumption

If planned consumption was 1,000 kg and the aircraft used 1,050 kg under comparable conditions, the observed factor is 1.05, equivalent to a positive five per cent bias. A future baseline burn of 2,000 kg would then become 2,000 × 1.05 = 2,100 kg before separately calculated reserves.

There is no single universal notation. One dispatch tool may request 1.05, another +5%, and an add-on may define the sign or ratio differently. Use the meaning stated by that tool rather than assuming the formula above is its required input. Base the factor on several comparable flights; one headwind, long taxi or poor power setting is not evidence of a permanent aircraft bias.

MSFS fuel calculator: what must it include?

An MSFS fuel calculator must use the selected aircraft variant, payload, route distance, planned altitude, winds, phase-specific fuel flow, taxi allowance and reserves.

• Aircraft and engine profile: a 737-700 profile is not interchangeable with another 737 variant, and a stock aircraft may differ from a detailed add-on.
• Payload and take-off mass: heavier loads usually increase climb and cruise consumption.
• Route and altitude: use the flown route rather than straight-line distance, including climb, descent and likely procedures.
• Wind-adjusted time: fuel is consumed over time, so a headwind usually increases cruise burn for the same distance.
• Correct fuel flow: distinguish total-aircraft flow from per-engine flow and use the unit expected by the calculator.
• Taxi and reserves: identify whether they are already included in the reported block figure.

Repeatable light-aircraft calculation

This fictional single-engine example shows a reusable method, not a recommended loading quantity. Assume the chosen profile and payload give the following flows at the planned altitude, with a 240 NM cruise segment and wind-adjusted groundspeed of 120 knots.

1. Climb: 0.3 h × 12 US gal/h = 3.6 US gal.
2. Cruise time: 240 NM ÷ 120 kt = 2.0 h.
3. Cruise fuel: 2.0 h × 9 US gal/h = 18.0 US gal.
4. Descent and approach: 0.3 h × 7 US gal/h = 2.1 US gal.
5. Trip fuel: 3.6 + 18.0 + 2.1 = 23.7 US gal.
6. Other components: add an illustrative 1.2 US gal for taxi, 1.2 US gal contingency and 6.8 US gal reserve.
7. Block fuel: 23.7 + 1.2 + 1.2 + 6.8 = 32.9 US gal.

Replace every example input with the simulated aircraft’s own performance data. Then check usable capacity, tank distribution and maximum mass before loading.

When should I use an aircraft EFB or dispatch tool?

Use a generic calculator for a simple default aircraft when you have credible phase fuel-flow figures and can model the route manually. Use the aircraft’s EFB, tablet or matched dispatch profile for an airliner or complex turboprop with custom performance, tank logic, centre-tank rules or a proprietary loading system.

A generated fuel plan does not always load the aircraft. Planning and physically applying the load may be separate actions, so confirm the result on the loading page and cockpit indications.

Aircraft-specific examples

Non-prescriptive example: TBM 930

Select the exact TBM 930 profile for the simulator and add-on being flown. Do not substitute figures from a different TBM model merely because the airframes look similar.

Use turboprop fuel flow for the intended power setting and cruise altitude; the high flow seen during climb is not a suitable cruise value. Include start and taxi consumption, then check the left and right wing-tank quantities, fuel selector or automatic tank-selection behaviour, and the unit shown by the aircraft. Some interfaces present Jet A by mass while others display US gallons.

Load symmetrically unless the aircraft’s own system instructs otherwise, and verify both tank indications after electrical power is established. This example deliberately gives no universal TBM 930 fuel quantity because route, payload, wind and modelled performance determine it.

Non-prescriptive example: Boeing 737-700

Choose a Boeing 737-700 profile matched to the specific add-on and engine configuration. Never copy the block fuel from a 737-800, 737 MAX or another variant without recalculating it.

Jet fuel flow is commonly shown per engine, so total cruise burn must account for both engines. Taxi and APU use also belong in the plan. The 737-700 has left and right main tanks plus a centre tank; use the add-on’s EFB or loader to follow its tank-loading sequence and balance rules rather than forcing quantities through the simulator menu.

A direct simulator fuel change may be rejected or redistributed by a detailed 737 add-on. If the value snaps back, use its loader and allow any simulated refuelling process to finish before checking total fuel, tank balance and gross mass.

How do I convert fuel mass and volume?

Convert mass and volume separately. A density value is needed only when converting between those two measurement types.

• kg = lb ÷ 2.20462
• lb = kg × 2.20462
• litres = US gallons × 3.78541
• US gallons = litres ÷ 3.78541
• litres = imperial gallons × 4.54609
• fuel mass = fuel volume × density

Useful planning approximations are about 0.80 kg per litre for Jet A and 0.72 kg per litre for aviation gasoline, but density varies with specification and temperature. A simulator may use a fixed value, so prefer the conversion shown by its loader. Do not enter 750 gallons in a field expecting 750 pounds, and do not treat US and imperial gallons as equal.

How do I refuel in MSFS, X-Plane and Prepar3D?

Use the simulator’s native loading page for default aircraft, but use the aircraft’s dedicated EFB or load manager whenever a complex add-on controls its own fuel state.

When the menus are unfamiliar, our guide to load managers and weight-and-balance screens explains the difference between native controls and aircraft-specific loaders.

Microsoft Flight Simulator 2020

1. Set the preflight load. From the World Map, select the aircraft and open its Weight & Balance settings. Enter the intended fuel and payload before starting the flight.
2. Adjust after loading if necessary. For supported default aircraft, open the top toolbar and use the Fuel panel. An instant menu change is not the same as requesting a fuel truck.
3. Use the add-on’s loader when supplied. Detailed aircraft may continuously replace values entered through the MSFS panel.
4. Verify in the cockpit. Compare total and individual tank indications with the requested block fuel.

Microsoft Flight Simulator 2024

1. Review fuel during preflight. MSFS 2024 places more route, performance and loading work in its integrated EFB and preflight interfaces than the World Map-first workflow used by MSFS 2020.
2. Open the fuel and payload function. Use the EFB or aircraft-loading page made available by the selected aircraft and activity. A complex aircraft may supply a separate tablet instead.
3. Apply the load. Calculating or displaying block fuel does not necessarily transfer it to the tanks; use the available load, apply or send function where one is provided.
4. Check mode restrictions. An activity or career scenario may control the available quantity or loading process differently from free flight.
5. Confirm the result. Check cockpit gauges, individual tank balance, gross mass and centre of gravity.

X-Plane

In X-Plane 12, use the Weight, Balance & Fuel controls available through Flight Configuration or the flight menu. X-Plane 11 uses its Edit Weight & Balance interface. Set fuel, payload and centre of gravity, then apply the changes and inspect the cockpit gauges.

The native control may set total fuel and distribute it according to the aircraft definition. If a third-party aircraft provides its own tablet or plug-in loader, use that instead; otherwise the custom systems may immediately restore their saved tank state.

Prepar3D

Open the menu bar and use Vehicle > Fuel and Payload, with wording varying slightly between Prepar3D generations. Set the listed tank quantities and payload, accept the change, and verify total mass and cockpit indications.

Complex Prepar3D aircraft commonly use an external setup utility, in-cockpit panel or EFB. A saved scenario may also restore an older fuel state when reloaded, so make the loading change after the scenario has finished initialising unless the aircraft’s instructions say otherwise.

How to refuel in FSX

FSX uses its built-in Aircraft > Fuel and Payload menu for default aircraft, with individual tank controls available through the Change Fuel dialog.

1. Load the aircraft and flight. The native menu can change fuel instantly, so the aircraft does not need to be beside a pump merely to edit its fuel state.
2. Reveal the menu bar. Press Alt if the FSX menu is hidden.
3. Open the loading window. Choose Aircraft > Fuel and Payload.
4. Select Change Fuel. Enter the required level for each listed tank using the quantity or percentage fields presented by FSX. Watch the displayed total fuel weight as the tank values change.
5. Distribute the target correctly. Keep paired wing tanks balanced unless the aircraft requires another arrangement. Do not place the whole block figure in every tank.
6. Apply the change. Confirm the Change Fuel window and then the main Fuel and Payload window.
7. Check the loaded amount. Reopen Fuel and Payload to confirm the total, then compare the individual tank quantities with the cockpit fuel gauges. In standard FSX installations, cycling the Shift+Z information display can provide an overall fuel percentage, but it does not replace tank-by-tank checks.

FSX does not calculate a valid block quantity merely because the tanks have been filled. Work out the target first, then use the menu to load it. Our additional FSX refuelling examples cover the menu, airport pumps and fuel-truck method.

Why does an FSX fuel quantity reset or show incorrectly?

If the number snaps back after closing the window, the aircraft’s panel or add-on is probably controlling the fuel state. Use its configuration utility, loading panel or in-cockpit fuel controls instead of the FSX menu.

• The saved quantity returns: a saved flight or aircraft state has restored its previous tanks. Apply the load after the aircraft finishes initialising, or save a new state through the add-on.
• The gauges do not move: some gauges need battery or avionics power, and an analogue gauge may respond slowly. Recheck the FSX Fuel and Payload total before assuming that loading failed.
• Total fuel is right but the aircraft rolls: the tanks are asymmetric. Correct the individual tank entries.
• The add-on reports a different unit: check pounds against kilograms and gallons against litres, and determine whether the field expects total fuel, per-tank fuel or uplift.
• Fuel never decreases: disable unlimited-fuel or fuel-assistance options. Those settings affect consumption even when the loaded quantity appears normal.

Why will an aircraft not refuel?

Most refuelling failures come from using the wrong loading interface, failing a ground-service condition or confusing target fuel with uplift.

• The value snaps back: use the aircraft’s EFB, tablet, FMS utility or custom loader.
• The plan shows fuel but the tanks do not: the fuel was calculated but not physically applied to the aircraft.
• The truck arrives but nothing transfers: set the parking brake, shut down engines if required, use a suitable stand and check that the aircraft supports that service.
• The quantity is wildly wrong: verify units and whether the field is total, uplift or a per-tank amount.
• The engines stop with fuel remaining: check selectors, pumps, crossfeed, mixture or condition levers. Fuel in an unselected or unusable tank cannot feed the engine.

After every load, verify total, usable and remaining fuel without mixing units before departure.

Why is fuel burn higher than planned?

Fuel burn normally exceeds the plan because the aircraft profile, payload, altitude, wind, speed or engine settings differ from the calculator’s assumptions.

For piston aircraft, common causes include an over-rich mixture at altitude and excessive power. For jets and turboprops, low cruise altitude, high speed, unexpected headwinds, prolonged anti-ice use, holding, APU operation and inefficient climb settings all add consumption.

Compare actual remaining fuel with the plan after climb and at regular route checkpoints. A shortfall that grows consistently under comparable conditions may justify a fuel factor; an isolated difference should be traced to weather, route or technique first.

How much reserve fuel should I carry?

There is no universal reserve amount for every simulator flight, aircraft and operating rule.

For casual simulation, allow for plausible delays and a diversion rather than planning to arrive nearly empty. When recreating real operations, apply the VFR, IFR or airline policy appropriate to that scenario and protect final reserve instead of treating it as ordinary trip fuel. Generic examples and simulator calculations must never be used for real-world flight planning.