Aviation unit converter.
Switch between the metric and imperial units that fill ATPL questions and the flight deck, including fuel volume to mass with a chosen density.
Aviation unit converter
Switch between the units that show up across ATPL study and the flight deck, distance, speed, altitude, mass, volume, pressure, temperature, and fuel volume ↔ mass.
Enter a value to convert.
In the EASA ATPL exam
Unit conversion is never its own question in the EASA ATPL, but it is buried inside hundreds of them. Mass and Balance (subject 031) hands you fuel in litres or gallons and a load sheet in kilograms or pounds; Flight Planning (033) and General Navigation (061) switch between nautical miles, kilometres and metres mid-question. The conversion is the step examiners expect you to do silently and correctly, and the wrong-factor answers are always sitting in the options.
Exam-style example
You uplift 6,000 litres of Jet A-1 with a fuel density of 0.78 kg/L. What mass goes on the load sheet, and what is that in pounds?
- Volume to mass: multiply by the density. 6,000 × 0.78 = 4,680 kg.
- Kilograms to pounds: multiply by 2.205. 4,680 × 2.205 ≈ 10,320 lb.
Fuel load = 4,680 kg, or about 10,320 lb.
Common trap: Dividing where you should multiply. Litres to kilograms is volume × density; kilograms to litres is mass ÷ density. The distractor built from the inverted operation (here 6,000 ÷ 0.78 ≈ 7,692) looks plausible and is usually one of the four options.
Aviation units explained
The definition, the formula, a worked example and how it shows up in the ATPL exams.
Aviation units explained
The definition, the formula, a worked example and how it shows up in the ATPL exams.Why units bite in the ATPL
European aviation runs on a mix of metric and imperial units that rarely line up neatly. Altitudes are in feet but runway lengths and visibility are often in metres; speeds are in knots but climb rates are in feet per minute; fuel is planned in kilograms but loaded in litres or US gallons. EASA ATPL questions deliberately mix these to test whether you can convert quickly and reliably under time pressure.
This converter keeps the common aviation units in one place so you can check an answer in seconds rather than fumbling a factor mid-exam.
The conversions worth memorising
A handful of factors come up again and again: 1 nautical mile = 1.852 km; 1 knot = 1.852 km/h; 1 foot = 0.3048 m; 1 kg = 2.205 lb; 1 US gallon = 3.785 L; 1 imperial gallon = 4.546 L; and the altimetry pair 1013.25 hPa = 29.92 inHg.
A flight level is just the pressure altitude in hundreds of feet flown on the standard 1013 setting, so FL100 is 10,000 ft pressure altitude. Knowing these cold removes a whole class of avoidable errors.
Fuel: volume to mass with a density
Aircraft performance and mass-and-balance work in mass (kilograms or pounds), but fuel is delivered by volume (litres or gallons). The bridge is density. Jet A-1 is typically around 0.80 kg/L, but it varies with temperature, so the dispatch figure on the fuel receipt is what counts.
Worked example: 5,000 L of Jet A-1 at 0.80 kg/L = 4,000 kg. Drop the density to 0.79 kg/L on a warm day and the same volume is only 3,950 kg, a 50 kg difference that matters for a tight mass-and-balance calculation.
Use it to build exam speed
Mass and Balance, Flight Planning, Performance and General Navigation all assume you can switch units instantly. Drill the common pairs (NM/km, kg/lb, ft/m, hPa/inHg) until they are automatic, then use this converter to check your manual work rather than to replace it.
Good to know
Background and tips for getting the most out of this calculator.
Good to know
Background and tips for getting the most out of this calculator.Fuel volume ↔ mass
Litres and gallons convert to kilograms and pounds through density. Jet A-1 is roughly 0.80 kg/L; always confirm with the load sheet.
Pressure pairs
1013.25 hPa equals 29.92 inHg. The converter keeps the altimetry pair consistent so subscale settings line up.
Exam speed
Drilling the common conversions, NM/km, kg/lb, ft/m, until they are instant removes a whole class of avoidable ATPL mistakes.
Frequently asked questions
Tap to read the full background and answers.
Frequently asked questions
Tap to read the full background and answers.- What units does this converter handle?
- Distance (NM, km, miles, m, ft), altitude (ft, m, flight level), speed (kt, mph, km/h, m/s, ft/min), mass, volume, pressure, temperature, and fuel volume ↔ mass.
- How does the fuel conversion work?
- Fuel volume to mass uses a density. Pick a preset (Jet A-1, Jet A, AVGAS, water) or enter a custom kg/L figure. Always use the load-sheet density for dispatch.
- How do I convert litres of jet fuel to kilograms?
- Multiply the volume in litres by the fuel density in kg/L. Jet A-1 is about 0.80 kg/L, so 5,000 L is roughly 4,000 kg. Always confirm the actual density on the day from the fuel paperwork.
- Why do I need a unit converter for ATPL?
- EASA ATPL questions mix metric and imperial units constantly, feet, metres, knots, kg, pounds, litres, gallons, hPa, inHg. Fast, reliable conversion saves time in the exam.
- What is the difference between a US gallon and an imperial gallon?
- A US gallon is 3.785 litres; an imperial gallon is 4.546 litres, about 20% more. ATPL fuel questions use both, and picking the wrong gallon produces one of the trap answers, so read the units in the question stem before touching the numbers.
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