Fuel Consumption Calculator
Instantly work out your car’s fuel efficiency in MPG, litres per 100km, and km/L, plus an estimated running cost for your journey.
Calculate Fuel Efficiency
Enter the distance you travelled and the fuel you used, and optionally a fuel price, to instantly see your car’s efficiency across every common unit, plus an estimated cost.
Fuel Efficiency Calculator
Get instant MPG, L/100km, and km/L results.
Understanding Fuel Economy
Key concepts for comparing and tracking efficiency
Litres per 100km
Used across most of Europe, this figure shows how much fuel is consumed over a fixed distance — lower numbers mean better efficiency.
Miles per Gallon (MPG)
Common in the UK and US, MPG shows how far a vehicle travels per unit of fuel — higher numbers mean better efficiency. Remember UK and US gallons differ in size.
Real-World vs. Official Figures
Manufacturer-quoted economy is measured under controlled lab conditions. Real-world driving, weather, and load typically produce a somewhat higher consumption figure.
Tracking Over Time
Recording distance and fuel used at every fill-up, and calculating consumption each time, gives a far more accurate picture than relying on a single reading.
Fuel Economy Rating Guide
A general guide to how different consumption figures compare for a typical petrol or diesel passenger car.
| Rating | Litres / 100km | MPG (UK) | MPG (US) | Typical Vehicle |
|---|---|---|---|---|
| < 4.0 | > 70 | > 59 | Hybrid / small city car | |
| 4.0 – 5.0 | 56 – 70 | 47 – 59 | Efficient compact car | |
| 5.0 – 6.5 | 43 – 56 | 36 – 47 | Family hatchback / saloon | |
| 6.5 – 8.0 | 35 – 43 | 29 – 36 | Mid-size SUV / estate | |
| 8.0 – 10.0 | 28 – 35 | 24 – 29 | Large SUV / performance car | |
| > 10.0 | < 28 | < 24 | Van, pickup, or high-performance vehicle |
Fuel Consumption FAQ
Answers to the most frequently asked questions about measuring and comparing fuel efficiency.
Divide the litres of fuel used by the distance travelled in kilometres, then multiply by 100. For example, using 40 litres to travel 500km gives (40 ÷ 500) × 100, which equals 8 litres per 100km. This calculator handles the maths automatically.
A UK (imperial) gallon is larger than a US gallon, roughly 4.546 litres compared to 3.785 litres. Because of this, the same car’s fuel economy will show a higher MPG figure in imperial gallons than in US gallons, even though the actual fuel used is identical.
For imperial MPG, divide 282.481 by the MPG figure. For US MPG, divide 235.215 by the MPG figure. Both formulas give the equivalent consumption in litres per 100 kilometres.
For a typical petrol family car, anything under about 6 litres per 100km (roughly 47 imperial MPG) is generally considered efficient, while under 5 litres per 100km (around 56 imperial MPG) is excellent. Hybrid and diesel vehicles often achieve lower figures still, and electric vehicles are measured differently, in energy per distance rather than fuel volume.
Official figures come from standardised lab tests under ideal conditions. Real-world factors — cold starts, traffic, hilly terrain, tyre pressure, roof racks, and driving style — all increase actual fuel consumption above the advertised number, often by 10–25%.