Fuel Mileage Calculator — MPG & L/100 km
Fill up your tank, drive, then fill up again. Enter the distance covered and the litres used to find your actual fuel economy in km/L, L/100 km and US mpg.
km
L
Kilometres your vehicle travels per litre of fuel
- 1
L/100 km equivalent
100 ÷ 15 km/L = 6.67The same efficiency expressed as fuel consumed per 100 km. - 2
Fuel efficiency (km/L)
300 km ÷ 20 L = 15
How does this calculator work?
Divide the distance you drove by the litres you used to get km/L; invert and multiply by 100 for L/100 km, or multiply km/L by 2.352 for US mpg. Measure over a full tank-to-tank trip for accuracy. Real-world figures are typically 15–25% below manufacturer ratings because lab tests use idealised conditions.
Formula
How this is calculated
To measure real-world fuel mileage, start with a full tank and note the odometer reading. Drive normally, then fill up again and note the litres added and the new odometer reading. Dividing the distance by the litres gives your fuel efficiency in km/L — the higher the number, the more efficient your vehicle.
The calculator converts the result to L/100 km (the most common unit in Europe and Australia) by inverting the ratio: L/100 km = 100 ÷ km/L. It also converts to US mpg using the factor 1 km/L ≈ 2.352 US mpg, so you can compare with North American ratings. Note that US mpg and Imperial (UK) mpg are different — 1 US gallon is 3.785 L while 1 Imperial gallon is 4.546 L.
The figure reflects your specific driving conditions on that trip — speed, load, terrain, climate and driving style all play a role. For a reliable long-term average, repeat the measurement over several fill-ups and average the results.
Frequently asked questions
Fill the tank completely, reset the trip meter, drive normally, then fill again. Divide the kilometres driven by the litres added at the second fill. Repeat over 3–5 fill-ups and average for a reliable figure.
A US gallon is 3.785 litres and an Imperial (UK) gallon is 4.546 litres. The same vehicle will show a higher number in UK mpg than US mpg: 1 US mpg ≈ 0.832 Imperial mpg.
Official ratings are measured in controlled lab conditions. Real driving in traffic, at highway speeds, with air conditioning and a loaded car is consistently less efficient — often 15–25% below the stated figure.
Also known as
TG we-Calculate Editorial Team. (2026). Fuel Mileage Calculator — MPG & L/100 km [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/fuel-mileage-calculator
TG we-Calculate Editorial Team. "Fuel Mileage Calculator — MPG & L/100 km." TG we-Calculate. 2026. https://we-calculate.com/calculator/fuel-mileage-calculator.
TG we-Calculate Editorial Team, "Fuel Mileage Calculator — MPG & L/100 km," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/fuel-mileage-calculator
@misc{wecalculate_fuel_mileage_calculator, title = {Fuel Mileage Calculator — MPG & L/100 km}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/fuel-mileage-calculator}}, year = {2026}, note = {TG we-Calculate} }
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