You just spawned into your aircraft, and the first question every new sim pilot asks is the same one: how much fuel do I load? So you drag the slider to 100%, fill every tank to the brim, and go flying. It works — but it is almost never what a real pilot does, and in MSFS 2024 career mode it can actively cost you money or leave you unable to take off at all.
This guide fixes that. We will cover how much fuel to actually load, for both light general aviation aircraft like the Cessna 172 and for airliners like the A320 and 737. We will do it in both kilograms and pounds, and both litres and US gallons, because fuel planning is one of the few areas of aviation where the units genuinely trip people up depending on where in the world you fly. By the end you will have a repeatable method instead of a guess.
This pairs naturally with our SimBrief to FMC workflow guide — SimBrief does the fuel maths for airliners, and this guide explains what those numbers mean and where they go.
How much fuel do I actually need in MSFS 2024?
Enough for the trip, plus legally-required reserves, plus a sensible buffer — almost never a full load. Full tanks add weight, which burns more fuel, lengthens your takeoff roll, and on many aircraft pushes you over your maximum weight before you have loaded a single passenger. Real fuel planning is a short sum: trip fuel + contingency + alternate + reserves + taxi = the total you load (the "block fuel").
The instinct to fill to 100% comes from car driving, where a full tank is free peace of mind. In an aircraft, fuel is weight, and weight has consequences on every phase of flight. A Cessna 172 with full tanks physically cannot carry four adults — it would be over its maximum takeoff weight. An airliner loaded with far more fuel than the sector needs burns extra fuel just carrying that fuel around.
So the goal is not "as much as possible." The goal is "enough, with a proper margin, and no more." The rest of this guide is how you land on that number.
What are the parts of a fuel plan?
Every fuel plan, from a light single to a widebody, is built from the same handful of components. Learn these five and you can plan any flight. Fuel is loaded as one total — the block fuel — but that total is the sum of clearly-defined parts, and understanding the parts is what lets you make sensible decisions in flight.
Here is the standard ICAO breakdown that SimBrief and every airline dispatcher uses:
- Taxi fuel — burned from engine start to the runway (and any APU use). Small for a light aircraft, several hundred kg for an airliner.
- Trip fuel — the fuel to fly from takeoff to landing at your destination. This is the big number, and it is simply flight time multiplied by fuel burn.
- Contingency fuel — a buffer for the unexpected: stronger headwinds than forecast, a re-route, or holding. For airliners the ICAO minimum is the greater of 5% of trip fuel or 5 minutes of holding.
- Alternate fuel — fuel to fly from your destination's missed-approach point to a diversion airport, if you have nominated one.
- Final reserve fuel — the untouchable minimum. Under ICAO/EASA rules this is 30 minutes of holding at 1,500 ft for turbine aircraft, or 45 minutes for piston-engined aircraft, at holding speed.
Add those together (plus any discretionary "extra" fuel the captain chooses to carry) and you get block fuel — the number you physically load. On the SimBrief OFP this appears as a neat table; in a light aircraft you do the same sum on the back of an envelope.
What are the legal fuel reserves — ICAO vs FAA?
There are two families of rules, and which one you follow depends on where you are flying and how. Outside the US, airlines follow ICAO/EASA fuel policy, which is built around contingency and a 30-minute (turbine) final reserve. In the US, light aircraft follow the FAA's simpler FAR 91.151 (VFR) and 91.167 (IFR) reserve minimums. The numbers are close but not identical, and it is worth knowing both.
The FAA rules are refreshingly blunt. For VFR flight (FAR 91.151), you need enough fuel to reach your first intended landing and then fly for at least 30 minutes by day, or 45 minutes by night, at normal cruising speed. For IFR flight (FAR 91.167), you need enough to reach the destination, then reach the alternate (if one is required), and then fly a further 45 minutes at normal cruising speed. "Normal cruising speed" means the burn you are actually using — not some worst-case figure.
The ICAO/EASA framework is more granular because it is aimed at commercial jets. Here is how the two compare:
| Reserve type | ICAO / EASA (airlines) | FAA Part 91 (GA) |
|---|---|---|
| Contingency | Greater of 5% of trip fuel or 5 min holding | Not separately required |
| Final reserve (turbine) | 30 min holding at 1,500 ft, holding speed | — |
| Final reserve (piston) | 45 min holding at 1,500 ft, holding speed | — |
| VFR reserve | — | 30 min day / 45 min night at cruise |
| IFR reserve | — | 45 min at cruise (after alternate) |
| Alternate fuel | To alternate after missed approach | To alternate when one is required |
For sim flying, you do not have to fly to any regulator's standard — MSFS will not fail you for landing with 20 minutes of fuel. But planning to a real reserve is what stops you running a tank dry over the outer marker, and it is the habit that makes flying online (VATSIM, IVAO) or career mode go smoothly.
How much fuel does a Cessna 172 need? (a simple GA workflow)
For a light single like the Cessna 172, fuel planning is a two-minute pencil exercise: estimate your flight time, multiply by burn, then add a reserve. The C172S holds 56 US gallons total and 53 US gallons usable (about 200 litres usable), and burns roughly 8 to 10 US gallons per hour in cruise. A common flight-planning figure is around 9 gph.
Let's plan a realistic cross-country. Say your route is 150 nautical miles and you expect a groundspeed of about 115 knots. That is roughly 1.3 hours in the air.
- Trip fuel: 1.3 hours × 9 gph ≈ 12 US gallons (about 45 litres).
- Taxi, run-up and climb allowance: add roughly 1.5 gallons (about 6 litres).
- Reserve (day VFR): 30 minutes at 9 gph = 4.5 gallons; for night VFR use 45 minutes = 6.75 gallons (about 26 litres).
That gives a day-VFR plan of around 18 gallons — call it 20 to keep it tidy. Against 53 usable gallons, you are carrying well under half tanks and still landing with a comfortable margin. There is no reason to fill to the brim, and a good reason not to, which we will get to in the weight-and-balance section.
A quick sanity check on burn: at 75% power the C172S burns close to 9.9 gph at around 124 knots; throttle back and 8 to 8.5 gph is realistic. Treat the POH numbers as a best case measured on a new engine in ideal conditions, and plan a little conservatively.
Photo: Senior Airman Zachary Perras, U.S. Air Force, public domain, via Wikimedia Commons
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How do I plan airliner fuel with SimBrief?
For jets, you do not do the maths by hand — you let SimBrief act as your dispatcher and read the block fuel off the Operational Flight Plan (OFP). SimBrief calculates trip, contingency, alternate, final reserve and taxi fuel using real performance data for your specific aircraft type, then sums them into a single block figure. Your job is to read that figure correctly and load it.
If you have not used SimBrief before, our SimBrief to FMC workflow guide walks through generating a plan end to end. Once generated, the OFP's fuel section looks something like this for a short-haul 737-800 (London to Barcelona, planned in kg because it is a European operator):
| Fuel component | Example (B738) | In pounds |
|---|---|---|
| Trip fuel | ~5,200 kg | ~11,500 lb |
| Contingency (5%) | ~260 kg | ~575 lb |
| Alternate | ~1,800 kg | ~3,970 lb |
| Final reserve | ~900 kg | ~1,985 lb |
| Taxi | ~200 kg | ~440 lb |
| Block fuel | ~8,360 kg | ~18,430 lb |
The block fuel is the only number you load into the aircraft; the rest are its ingredients. Note the units: a Ryanair or easyJet-style European operator plans in kilograms, while a US carrier flying the same jet would show every one of those figures in pounds. Neither is more correct — but you must know which one your OFP is in before you type anything into the aircraft, because a kg figure entered into a lb field (or vice versa) is roughly a factor-of-two error.
Two components deserve special attention in the sim. Contingency is routinely burned into on a bad-wind day, so it is normal to land with less than planned — that is what it is for. Final reserve is the line you never cross; if the FMC is predicting you will land below it, you have a real problem and should be thinking about a diversion.
Where do I enter fuel and weights in the A320 and 737?
Fuel and weight go into two different places on each aircraft: a physical load (via the EFB or sim menu) and a set of numbers typed into the flight management computer. On the Airbus A320 that computer page is INIT B; on the Boeing 737 it is PERF INIT. Getting these to agree with what is physically in the tanks is the single most common source of wrong V-speeds and bad fuel predictions.
On the A320 MCDU, press the right-arrow from the INIT A page to reach INIT B. This is the weight-and-fuel page: you enter ZFW/ZFWCG (zero fuel weight and its centre of gravity, in tonnes, e.g. 60.5/27.0) and the BLOCK fuel. The MCDU also shows a TAXI figure (a default, often 200 kg / 400 lb) and reserve fields. Once ZFW and block are both in, the FMGC derives your gross weight and starts producing fuel predictions. In flight, those predictions live on the separate FUEL PRED page. If you want to drill this without loading the sim, our free A320 MCDU Trainer walks you through INIT B and the rest of the pages keystroke by keystroke, and the A320 MCDU explained guide covers every page in detail.
On the Boeing 737 FMC, the equivalent is the PERF INIT page. You enter ZFW (or gross weight), RESERVES, COST INDEX and CRZ ALT. Weights are in thousands — 62.5 means 62,500 — in either kg or lb depending on how the aircraft is configured, so check the unit shown on the page. The FMC reads the fuel already loaded in the tanks automatically and adds it to your ZFW to compute gross weight, so you do not type the fuel figure here; you load it physically first. One trap worth knowing: enter only your alternate-plus-final-reserve in the RESERVES field, not contingency, or you will get nuisance "USING RSV FUEL" messages every time you dip into contingency in the normal course of the flight. Our free 737 CDU Trainer lets you practise PERF INIT the same way.
The golden rule for both: the number in the FMC must match what is actually in the tanks, not necessarily what SimBrief planned. If SimBrief said 8,360 kg but you loaded 8,400, use 8,400.
How do I load fuel in the MSFS 2024 UI?
For any aircraft, MSFS 2024 loads fuel through the Weight & Balance interface — either the built-in one or the aircraft's own EFB — using sliders you set and then apply. Since Sim Update 4, the load sliders show value labels so you can see exactly what you are setting, and the aircraft's Maximum Zero-Fuel Weight is enforced so the interface will not let you overload the cabin.
The generic path is the Weight & Balance page reachable from the in-sim toolbar: it has tabs for fuel and for payload (seats and cargo). Set the fuel slider to the quantity you planned, set your passengers and cargo, then apply it — on aircraft EFBs this is usually a "Load in Aircraft" button, and nothing changes in the tanks until you press it.
A few things that catch people out:
- Units are a setting, and the EFB is independent of the FMC. The EFB can be toggled between kg and lb in its own settings menu, while the FMC often works in tonnes. Set the EFB to match the units on your SimBrief OFP before you start dragging sliders.
- Study-level aircraft override the default menu. The PMDG 737, Fenix A320 and FlyByWire A32NX all expect you to load fuel through their own EFB, and the native MSFS fuel menu may not work correctly with them. Use the aircraft's EFB for those.
- Load fuel before you program the FMC, so the FMC reads the correct on-board quantity when you set up the performance pages. Our full EFB guide covers the Weight & Balance page in more depth, including on Xbox and PS5.
kg or lbs? litres or gallons? Handling units without the headache
The units question is the one that genuinely bites sim pilots, because aviation mixes mass and volume and mixes metric and imperial depending on the operator and the fuel truck. Airliners are planned and loaded by mass (kg outside the US, lb inside it); light aircraft fuel is usually measured by volume at the pump (litres in most of the world, US gallons in America). You will meet all four.
Here is the conversion cheat-sheet worth keeping next to your monitor:
| Convert | Multiply by | Example |
|---|---|---|
| kg → lb | 2.205 | 8,000 kg = 17,640 lb |
| lb → kg | 0.4536 | 18,000 lb = 8,165 kg |
| US gallons → litres | 3.785 | 53 US gal = 200.6 L |
| litres → US gallons | 0.264 | 200 L = 52.8 US gal |
| US gallons → imperial gallons | 0.833 | 53 US gal = 44.1 imp gal |
| Avgas 100LL: US gal → lb | 6.0 | 53 US gal ≈ 318 lb (144 kg) |
| Jet A: US gal → lb | 6.7 | 100 US gal ≈ 670 lb (304 kg) |
Two density facts convert volume to weight: Avgas 100LL weighs about 6.0 lb per US gallon (0.72 kg per litre), and Jet A weighs about 6.7 lb per US gallon (0.80 kg per litre), both at the standard 15°C. That is why an airliner's tanks are quoted in kg or lb but the fuel truck bill is in litres or gallons — someone multiplied by density along the way.
Practical advice: pick one unit system and make SimBrief, the EFB and the FMC all agree. A single mismatch — kg into a lb field — gives you V-speeds calculated for an aircraft half its real weight, which is one of the most dangerous errors you can make on takeoff.
How does fuel tank selection work in GA aircraft?
Light aircraft do not draw from one big tank — you select which tank (or tanks) feed the engine, and getting this wrong is a classic cause of fuel starvation with plenty of fuel still on board. The Cessna 172 fuel selector has four positions: BOTH, LEFT, RIGHT, and OFF. High-wing Cessnas gravity-feed from tanks in each wing, and the normal position for flight is BOTH, which draws from both wings at once.
On the 172 you fly on BOTH for essentially the whole flight. You would only select an individual tank to manage a fuel imbalance — one wing sometimes feeds slightly faster than the other — and even that is optional. There is no requirement to switch tanks on a fixed schedule on the standard 172, so ignore any "switch every 30 minutes" advice you may have picked up; that comes from other aircraft types.
Low-wing aircraft are different and this is where sim pilots get caught. A low-wing type such as a Piper does not have a BOTH position, because the tanks sit below the engine and fuel has to be pumped, not gravity-fed. On those aircraft you must actively manage the tanks — flying on the left tank for a period, then switching to the right to keep the aeroplane in balance and to use all your fuel. If you fly a low-wing single or twin in MSFS and the engine quits with fuel showing, the selector is the first thing to check.
Why does career mode spawn me with so little fuel?
Because career missions load a preset fuel state that is often partial — sometimes surprisingly low — rather than full tanks. Players have repeatedly reported bush and cargo missions (the DHC-2 Beaver and Cessna Caravan come up a lot) spawning with only a fraction of a tank, and in some cases the aircraft defaults to drawing from the left tank only, which makes the usable fuel look even worse than it is.
This is a known friction point, and there are a few practical fixes:
- Check the fuel selector first. If the aircraft has spawned on LEFT only, move it to BOTH so it draws from all tanks. This alone solves a lot of "not enough fuel" reports.
- Bind an add-fuel key. MSFS has a control you can bind that adds a chunk of fuel (around 25% of tank capacity per press) — useful when a mission is genuinely short on fuel.
- Use the EFB fuel tab where the mission allows it. Some missions let you adjust fuel in the EFB before departure; others lock the fuel fields, so this does not always work.
The deeper point is that career mode makes fuel a resource with a cost, which is exactly why fuel planning matters there in a way it does not in free flight. Loading only what the leg needs, rather than full tanks every time, is part of running a profitable operation — our career mode money guide covers the economics side of that.
Why can't I fill the tanks AND load full payload?
Because full fuel plus full cabin usually exceeds the aircraft's maximum takeoff weight — every aircraft has a fixed weight budget you split between fuel and payload. This is the single most important weight-and-balance concept, and it is why "just fill it to 100%" is not a strategy.
Take the Cessna 172S. Its maximum takeoff weight is 2,550 lb (1,157 kg). A typical empty 172S weighs around 1,680 lb, leaving a useful load of roughly 870 lb to divide between fuel and everything else. Full usable fuel (53 gallons of Avgas) weighs about 318 lb (144 kg) — so with full tanks you are left with only around 550 lb for people and bags. That is two average adults and light luggage, not four adults. To carry four people you must take off with less than full fuel. There is no way around the arithmetic; the wing can only lift so much.
The same principle scales to airliners, expressed as three limits:
- MTOW (Maximum Takeoff Weight) — the most the aircraft may weigh at brake release.
- MZFW (Maximum Zero Fuel Weight) — the most the aircraft may weigh with no usable fuel; everything above this must be fuel, which is why MSFS enforces MZFW on the payload sliders.
- MLW (Maximum Landing Weight) — the most it may weigh on touchdown, which is why long-haul jets sometimes cannot land shortly after a heavy takeoff without burning or dumping fuel.
So on a heavy jet, tankering extra fuel "just in case" can force you to leave payload (passengers or cargo — i.e. revenue) behind. Load the fuel the flight needs plus a sensible reserve, and use the weight you save for the payload that actually pays. That trade-off is real aviation, and MSFS 2024 models it faithfully enough that planning fuel properly genuinely changes how your flights turn out.
Putting it together
Fuel planning is not the dark art it looks like from the cockpit with a fuel slider in front of you. It is one small sum — trip fuel, plus reserves, plus a buffer — done in whatever units your operator uses, and then loaded so the aircraft, the EFB and the FMC all agree.
Start small. Plan a C172 cross-country by hand: work out the time, multiply by nine, add a reserve, and load exactly that. Then let SimBrief do the same job for an airliner and read the block fuel off the OFP. Within a few flights you will stop reaching for 100% fuel automatically, and you will understand exactly why real pilots almost never do. To practise the FMC side of it, our free A320 MCDU Trainer and 737 CDU Trainer let you drill the fuel and weight pages in your browser before you ever start an engine.
