Aviation & Marine Calculator Suite

Last updated: 22 October 2026 · By Sardar Zain, Founder of Orixiva · Reading time: 6 minutes

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What the aviation fuel calculator includes

The aviation fuel calculator contains 7 separate tools. Choose one from the menu at the top of the page; each tool keeps its own inputs and explains the formula it uses.

How to use the aviation fuel calculator

1. Choose a tool. Select the calculation you need from the aviation fuel calculator menu.
2. Check the units. Pick the units you are working in before typing numbers, so the formula uses the right values.
3. Enter your values. Fill in every required field. Example values show the expected format.
4. Calculate and review. Read the main result, the breakdown and any notes or charts under it.
5. Save or compare. Copy, print or download the result, or change one input to compare scenarios.

Who uses this aviation fuel calculator?

• Student and private pilots planning cross-country flights.
• Boat owners estimating fuel for a passage.
• Flight schools and instructors preparing exercises.
• Marine and aviation hobbyists.
• Anyone converting knots and nautical miles.

Tips for accurate results with the aviation fuel calculator

• Always add legal reserve fuel on top of trip fuel; the fuel reserve tool helps.
• Use ground speed, not true airspeed, when headwind or tailwind is significant.
• Fuel density changes with temperature; convert by weight for heavy aircraft.
• For boats, fuel burn rises sharply above hull speed.
• These results are planning estimates and do not replace official flight planning or your aircraft manual.

Aviation fuel calculator guide: formulas, units and worked examples

Pilots and skippers plan fuel the same way: work out how long the trip takes, multiply by how fast the engine burns fuel, then add a reserve. This guide explains each step behind the aviation fuel calculator, gives unit conversions and works through examples for an aircraft and a boat. It is a planning aid only; always follow your flight manual, vessel documentation and local rules.

The four core formulas

Fuel by volume and by weight

Small aircraft and boats plan fuel in litres or gallons, but aircraft performance depends on weight. Avgas weighs about 0.72 kg per litre (about 6 lb per US gallon) and Jet A about 0.80 kg per litre (about 6.7 lb per US gallon). Marine diesel is about 0.84 kg per litre and petrol about 0.74 kg per litre. Density falls as fuel warms, so a full tank on a hot day holds slightly less mass.

Worked example 1: light aircraft trip with wind

A trainer cruises at a true airspeed of 105 knots and burns 28 litres per hour. The trip is 180 nautical miles with a 15-knot headwind component.

1. Ground speed: 105 − 15 = 90 knots.
2. Time: 180 ÷ 90 = 2.0 hours.
3. Trip fuel: 2.0 × 28 = 56 litres.
4. Reserve: 45 minutes at 28 L/h = 21 litres.
5. Taxi, climb and contingency: add about 10% of trip fuel, 5.6 litres, plus 3 litres for start and taxi.
6. Total: 56 + 21 + 5.6 + 3 ≈ 86 litres, or about 62 kg of avgas.

The return leg with a 15-knot tailwind runs at 120 knots, takes 1.5 hours and needs only 42 litres of trip fuel. Wind changes time, and time changes fuel.

Worked example 2: endurance and range

With 120 litres of usable fuel and a burn of 28 L/h, endurance is 120 ÷ 28 = 4.3 hours. Keeping a 45-minute reserve leaves 3.5 hours of flying, which covers about 315 nautical miles at a ground speed of 90 knots, or 420 nautical miles at 120 knots.

Worked example 3: motor boat run

A planing boat cruises at 22 knots and burns 38 litres per hour. A 33 nautical mile run takes 1.5 hours and uses 57 litres each way, 114 litres for the round trip. Using the common rule of thirds, that should be no more than two thirds of what you carry, so plan for at least 171 litres on board. A 2-knot current against you on the way back adds about 10% to the time and fuel of that leg.

Worked example 4: hull speed

A displacement sailboat with a waterline length of 30 feet has a hull speed of about 1.34 × √30 = 7.3 knots. Pushing a displacement hull past that speed makes it climb its own bow wave, so fuel burn rises steeply for very little extra speed. Cruising at 6 knots instead of 7 can cut fuel use by a third or more.

Worked example 5: fuel cost

If avgas costs 2.80 per litre, the 86 litres in example 1 cost about 241. Jet A at 1.60 per litre for a turboprop burning 250 litres per hour costs 400 per flying hour in fuel alone. The fuel consumption tool shows cost per trip and per hour so you can compare routes and cruise settings.

Unit conversions used in fuel planning

• 1 nautical mile = 1.852 km = 1.1508 statute miles
• 1 knot = 1.852 km/h = 1.1508 mph
• 1 US gallon = 3.785 litres; 1 imperial gallon = 4.546 litres
• 1 kg = 2.2046 lb
• 1 foot = 0.3048 metres

Reserve rules at a glance

Under US rules, airplanes flying VFR need enough fuel to reach the first point of intended landing plus 30 minutes by day or 45 minutes at night. IFR flights need fuel to the destination, then to an alternate, plus 45 minutes. Other countries follow similar ICAO-based rules, and airlines add contingency and final reserve fuel by regulation. For boats there is no single legal rule in most places, which is why many skippers use the rule of thirds or keep at least 20% in reserve.

Planning tips

• Use your own measured burn rate at the power setting you actually fly or cruise at.
• Plan with forecast winds and currents, then update the plan on the day.
• Dip or sight-check tanks before departure instead of trusting the gauge alone.
• Write the planned fuel at each waypoint on your log and compare as you go.

The FAA Pilot's Handbook of Aeronautical Knowledge covers fuel planning, weight and balance and performance in more detail.

7 fuel planning mistakes the aviation fuel calculator helps you avoid

Most fuel problems in small aircraft and boats come from a few simple slips rather than hard maths. The aviation fuel calculator is built to catch them, but it helps to know what to look for.

1. Mixing volume and weight. Fuel is sold in litres or gallons, but weight and balance uses pounds or kilograms. Avgas weighs about 6 lb per US gallon and Jet A about 6.7 lb per US gallon. Pick the right fuel type so the weight figure is correct.
2. Planning with still-air time. A headwind lowers your ground speed and adds time, and time is what burns fuel. Always enter the wind or use ground speed, not true airspeed.
3. Forgetting taxi and climb. Engines burn more fuel on the ground run and in the climb than in cruise. Add a fixed allowance for start, taxi and climb on every leg.
4. Ignoring unusable fuel. Part of every tank cannot reach the engine. Subtract the unusable amount listed in the aircraft or boat manual before you work out endurance.
5. Using the wrong gallon. An imperial gallon is about 1.2 US gallons. If your manual or fuel receipt is in imperial gallons, convert first.
6. Treating the reserve as spare fuel. The reserve is for the unexpected, such as a diversion or a hold. Plan to land with it still in the tanks.
7. Not rechecking in flight. Compare actual fuel used against the plan at each checkpoint. If burn is higher than planned, update the aviation fuel calculator with the real figure and decide early.

Quick check: one leg, start to finish

A light aircraft plans a 180 NM leg at 110 knots true airspeed with a 15 knot headwind. Ground speed is 95 knots, so the leg takes 180 ÷ 95 = about 1.89 hours (1 h 54 min). At 9 US gallons per hour that is about 17.1 gallons. Add 4.5 gallons for a 30-minute reserve and 1.5 gallons for taxi and climb, and the minimum fuel on board is about 23.1 US gallons, plus any unusable fuel.

Reserve rules depend on where and how you fly. In the United States, the FAA sets day VFR at 30 minutes and night VFR at 45 minutes in 14 CFR 91.151. Boaters often use the rule of thirds: one third out, one third back, one third in reserve. This aviation fuel calculator is a planning aid only; always follow your aircraft or boat manual and the rules that apply to you.

Privacy and accuracy

The aviation fuel calculator runs entirely in your browser. Numbers you type are not sent to Orixiva or stored on a server.

Results use standard published formulas and are rounded for display. They are estimates for planning, study and everyday decisions; for legal, medical, engineering or financial decisions, confirm them with a qualified professional. For background reading, see the Federal Aviation Administration.

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