MPG Converter
Enter a fuel economy value in any unit, US miles per gallon, UK miles per gallon, litres per 100 kilometres, kilometres per litre, or miles per litre, and every other unit updates instantly. Add a fuel price to calculate your cost per mile, cost per kilometre, and cost per 100 km. Switch the input mode to start from any unit.
Formula
Worked example
A car rated at 30 US mpg: L/100 km = 235.215 / 30 = 7.84 L/100 km; UK mpg = 282.481 / 7.84 = 36.03 UK mpg; km/L = 100 / 7.84 = 12.76 km/L; mi/L = 30 / 3.785 = 7.93 mi/L.
Why fuel economy units differ by country
The United States and the UK historically measure fuel economy in miles per gallon, but a US gallon (3.785 litres) and a UK (imperial) gallon (4.546 litres) are not the same volume. That 20% difference means a car rated at 30 US mpg shows 36 UK mpg for exactly the same journey, which is a source of confusion when comparing car specifications across markets. Most of Europe, Canada, and Australia instead report fuel consumption rather than economy, using litres per 100 kilometres, which is an inverse: a lower number means less fuel used and better efficiency. Japan and several Asian markets use kilometres per litre, which is analogous to mpg but metric.
How to convert between fuel economy units
The central conversion factor for US mpg is 235.215 (derived from 100 times the number of litres in a US gallon divided by kilometres per mile). Dividing 235.215 by any US mpg value gives the L/100 km equivalent, and dividing again by 100 gives km/L. For UK mpg the constant is 282.481, calculated from the larger UK gallon. To convert L/100 km to km/L, divide 100 by the L/100 km value. Because L/100 km is an inverse measure, better fuel efficiency is a lower number, while for mpg and km/L a higher number is better.
What counts as good fuel economy?
In the US, the EPA considers 28 mpg or above to be the rough average for new passenger cars, and vehicles rated above 40 mpg are classed as high-efficiency. Hybrid and plug-in hybrid vehicles routinely reach 50-56 mpg, while conventional petrol SUVs and trucks often fall to 15-22 mpg. In European terms, 6 L/100 km or below is considered excellent for a petrol engine, 6-8 L/100 km is good, and above 12 L/100 km is typical of heavier or less efficient vehicles. In India the government-mandated fuel efficiency standard (CAFE) targets 17-23 km/L depending on vehicle mass.
Estimating fuel cost from fuel economy
Once you know your fuel economy in L/100 km, the fuel cost for any journey is simple: multiply L/100 km by the distance in km, divide by 100 to get litres consumed, then multiply by the price per litre. For example, at 8 L/100 km over a 400 km trip you would use 32 litres; at 1.80 per litre that is 57.60 in fuel. The calculator above does this for you once you select a fuel price unit and enter a price. Cost-per-mile or cost-per-km outputs are useful for comparing the running cost of different vehicles or for reimbursement calculations.
Fuel economy benchmarks by vehicle type
| Vehicle type | US mpg | L/100 km | km/L | Economy rating |
|---|---|---|---|---|
| Hybrid sedan (e.g. Prius) | 50-56 | 4.2-4.7 | 21-24 | Exceptional |
| Compact car / economy | 32-40 | 5.9-7.4 | 13.5-17 | Excellent |
| Midsize sedan | 25-32 | 7.4-9.4 | 10.6-13.5 | Good |
| Large sedan / minivan | 18-25 | 9.4-13.1 | 7.6-10.6 | Average |
| Crossover SUV (small) | 22-30 | 7.8-10.7 | 9.3-12.7 | Good |
| Midsize SUV / 4WD | 16-24 | 9.8-14.7 | 6.8-10.2 | Below average |
| Full-size SUV / truck | 10-18 | 13.1-23.5 | 4.3-7.6 | Poor |
| Sports car | 15-28 | 8.4-15.7 | 6.4-11.9 | Varies |
Approximate real-world fuel economy ranges. Actual values vary by driving style, speed, and conditions.
Frequently asked questions
What is the difference between US mpg and UK mpg?
Both measure miles per gallon, but the gallon is different. A US gallon is 3.785 litres while a UK (imperial) gallon is 4.546 litres, making the UK gallon about 20% larger. A car rated at 30 US mpg is equivalent to 36.03 UK mpg on the same road. Always check which gallon a specification refers to, because mixing them up leads to a 20% error.
How do I convert mpg to L/100 km?
Divide 235.215 by the US mpg value. For example, 30 US mpg is 235.215 / 30 = 7.84 L/100 km. For UK mpg, divide 282.481 by the UK mpg value instead, because the UK gallon is larger. The calculator above handles both automatically.
How do I convert L/100 km to km/L?
Divide 100 by the L/100 km figure. For example, 7.84 L/100 km equals 100 / 7.84 = 12.76 km/L. The two units have an inverse relationship, so a lower L/100 km always corresponds to a higher km/L.
Why does UK mpg look better than US mpg for the same car?
Because the UK gallon holds 4.546 litres while the US gallon holds only 3.785 litres, a car travels more miles on a UK gallon simply because it contains more fuel. The actual fuel efficiency is identical; only the number changes when you switch gallon sizes. The ratio is always 1 US mpg = 1.20095 UK mpg.
How do I calculate fuel cost per mile from L/100 km?
Convert L/100 km to litres per kilometre by dividing by 100, then multiply by the price per litre to get cost per kilometre. Multiply cost per km by 1.60934 to get cost per mile. For example, 8 L/100 km at 1.80/L gives 0.08 x 1.80 = 0.144 per km, or 0.232 per mile. The calculator does this in one step when you enter a fuel price.
What is a good fuel economy in km/L?
For a standard petrol car, 12-17 km/L is considered good to excellent. Hybrids typically reach 21-24 km/L. Below 8 km/L is typical of larger SUVs, trucks, and older engines. In India, government CAFE standards target 17-23 km/L depending on vehicle weight, so 17 km/L or above is a rough benchmark for a fuel-efficient new car in that market.