Litres per 100 km to MPG UK Converter
Convert L/100 km into UK miles per gallon, US miles per gallon, km per litre and estimated fuel cost using the inverse fuel-consumption formula.
Enter The Fuel Consumption Figure
Converted Fuel Economy
This result is specific to a UK gallon, so it will be higher than a US mpg result for the same L/100 km value.
What This Converter Answers First
Many European car brochures, trip computers and hire-car listings show fuel consumption as litres per 100 kilometres. UK drivers often think in miles per imperial gallon, especially when comparing an older car, a used-car advert, a company vehicle or a quoted real-world economy figure. This converter gives the direct UK mpg answer first, then shows the US mpg and km/L values so that you can spot when a foreign review, forum post or manual is using a different gallon.
The conversion is not a simple multiplication by a small fixed number because L/100 km and mpg face in opposite directions. A lower L/100 km number is better, while a higher mpg number is better. That inverse relationship is the main reason people get strange answers when they try to convert fuel economy by memory. For example, reducing consumption from 8 to 6 L/100 km raises the UK mpg result from about 35.31 to 47.08. The two-unit change does not add a constant mpg amount at every point.
Fuel Cost Worked Example
Start with the L/100 km figure. Suppose a car averages 6.5 L/100 km in mixed driving. The converter reads this as the amount of fuel needed for each 100 kilometres, not as a tank size or hourly use.
Convert to UK mpg. The UK gallon conversion gives 43.46 UK mpg before rounding to two decimal places. A US review of the same car would show about 36.19 US mpg, because the US gallon is smaller.
Add a distance and fuel price. Over 12,000 km at 1.49 GBP per litre, the fuel-use check estimates 780 litres and a fuel spend of GBP 1,162.20. This is not a pump receipt prediction; it is a clean calculation from the consumption figure you entered.
Read the result beside your own driving. Motorway speed, short cold starts, tyre pressure, roof boxes, load, weather, EV-style mild hybrid behaviour and towing can all move real fuel use away from the quoted figure.
Conversion Formula And Method
The page uses the litre, kilometre, mile and gallon definitions behind the following formula. Each formula is shown on its own line so you can audit the calculation.
UK mpg = 282.4809363 / L per 100 km
US mpg = 235.214583 / L per 100 km
km per litre = 100 / L per 100 km
Fuel used in litres = distance in km x L per 100 km / 100
Fuel cost = fuel used in litres x fuel price per litre
The constant for UK mpg is larger because one UK imperial gallon is 4.54609 litres. The constant for US mpg uses 3.785411784 litres per US liquid gallon. Both use the same mile and kilometre relationship. The converter keeps the internal calculation unrounded, then applies your chosen display rounding at the end. That means the reverse check may show a tiny difference if you copy a rounded mpg number into another converter.
Quick Conversions
| L/100 km | UK mpg | US mpg | km/L | Plain-English Reading |
|---|---|---|---|---|
| 3.5 | 80.71 | 67.20 | 28.57 | Very efficient for a combustion car; often hybrid or small diesel territory. |
| 4.5 | 62.77 | 52.27 | 22.22 | Strong motorway or mixed-use economy for many UK drivers. |
| 5.5 | 51.36 | 42.77 | 18.18 | Common for efficient family cars when driven steadily. |
| 6.5 | 43.46 | 36.19 | 15.38 | Typical mixed result for a petrol family car or compact SUV. |
| 8.0 | 35.31 | 29.40 | 12.50 | Higher consumption; fuel price and annual mileage start to matter more. |
| 10.0 | 28.25 | 23.52 | 10.00 | Large petrol car, van, towing, roof load or repeated urban use may sit here. |
UK MPG, US MPG And Real-World Driving
UK mpg means miles per imperial gallon. US mpg means miles per US liquid gallon. A UK mpg number is about 20 percent higher than the US mpg number for the same L/100 km input, so it is easy to misread an American review as worse than it is or a UK advert as better than a US listing. When you compare two vehicles, keep every figure on one unit system before drawing a conclusion.
Published fuel figures are measured under set test procedures, while a real car on a real road is affected by traffic, terrain, speed, tyre choice, service condition and load. The converter is best used for unit conversion, annual fuel budgeting and advert comparison. It should not be used to challenge an official emissions value, calculate tax from CO2 bands or assume a guaranteed pump cost. For tax or emissions checks, use the official route for the vehicle and its registration data.
Useful Checks Before You Trust A Fuel Figure
- Confirm whether the original number is L/100 km, UK mpg or US mpg.
- Check if the value is WLTP, an owner-reported average, a dashboard reading or a single trip.
- Use your own annual distance and local fuel price for the cost line.
- For plug-in hybrids, separate petrol use from electricity use; this page only converts liquid-fuel consumption.
- For vans or towing, run a second case with a higher L/100 km value to see the cost sensitivity.
FAQs
Is 1 L/100 km really 282.48 UK mpg?
Yes. It is a mathematical conversion from litres per 100 kilometres to miles per imperial gallon. It is an extreme economy value rather than a typical road-car value, but the arithmetic is correct.
Why is the UK mpg result higher than the US mpg result?
A UK imperial gallon contains 4.54609 litres, while a US liquid gallon contains 3.785411784 litres. More litres per gallon means more miles can be assigned to one UK gallon for the same fuel consumption.
Can I convert mpg back to L/100 km?
Yes. For UK mpg, use L/100 km = 282.4809363 / UK mpg. The result panel includes a reverse check so you can see that the entered L/100 km value has been preserved after conversion.
Does this page handle electric vehicles?
No. EV energy use is normally shown as kWh per mile, miles per kWh or kWh per 100 km. A liquid-fuel mpg converter is not suitable for battery-electric running costs.
What rounding should I use for a used-car advert?
One decimal place is usually enough for comparing adverts. Two decimal places are useful when checking a calculation or reproducing a published conversion table. Whole mpg is fine for casual reading.
Why does my dashboard differ from the converter?
The converter only changes units. Your dashboard may average over a different distance, use a trip reset, apply manufacturer rounding or include recent cold starts and idling. Convert the same original value before comparing.
Sources
Bureau International des Poids et Mesures. (2019). The International System of Units (SI Brochure). BIPM. https://www.bipm.org/en/publications/si-brochure
National Institute of Standards and Technology. (2008). Guide for the Use of the International System of Units (NIST Special Publication 811). NIST. https://www.nist.gov/pml/special-publication-811
Driver and Vehicle Licensing Agency. (n.d.). Vehicle tax rates. GOV.UK. https://www.gov.uk/vehicle-tax-rate-tables