Fuel Economy Converter

Convert Fuel Economy Units Online — MPG, L/100km, and km/L

Our free fuel economy converter lets you instantly switch between miles per gallon, liters per 100 kilometers, and kilometers per liter so you can compare vehicle efficiency across any standard. Whether you are shopping for a car in another country, analyzing fleet fuel costs, or evaluating electric vehicle equivalents, this tool delivers accurate results in real time. All calculations run directly in your browser with no sign-up required and no data sent to any server.

How to Convert Between Fuel Economy Units

Fuel economy conversion is slightly more complex than simple unit conversion because some metrics measure distance per unit of fuel while others measure fuel per unit of distance. This inverse relationship means you cannot simply multiply by a single factor in all cases. Below are the key formulas and step-by-step examples for the most common fuel economy conversions.

MPG (US) to L/100km

The formula is L/100km = 235.215 / MPG (US). Because MPG measures distance per fuel unit and L/100km measures fuel per distance unit, the relationship is inverse. You divide the constant 235.215 by the MPG value. For example, a car rated at 30 MPG (US) consumes 235.215 / 30 = 7.84 L/100km. A vehicle achieving 25 MPG (US) uses 235.215 / 25 = 9.41 L/100km. The constant 235.215 comes from the number of liters in a US gallon (3.78541) multiplied by the number of kilometers in 100 miles (160.934), divided by 100 and then inverted.

L/100km to MPG (US)

The formula is MPG (US) = 235.215 / L/100km. The same constant works in both directions because of the inverse relationship. For example, a European car rated at 6 L/100km achieves 235.215 / 6 = 39.2 MPG (US). A vehicle consuming 10 L/100km gets 235.215 / 10 = 23.5 MPG (US). You can also use our dedicated L/100km to MPG converter for quick single-direction conversions.

MPG (US) to km/L

The formula is km/L = MPG (US) × 0.425144. Multiply the US MPG value by 0.425144 to get kilometers per liter. For example, 30 MPG (US) equals 30 × 0.425144 = 12.75 km/L. This conversion factor comes from dividing the number of kilometers in a mile (1.60934) by the number of liters in a US gallon (3.78541). The km/L metric is commonly used in Japan, India, and several South American countries.

MPG (US) to MPG (UK)

The formula is MPG (UK) = MPG (US) × 1.20095. The imperial gallon is larger than the US gallon, so a vehicle always has a higher MPG number when measured in imperial gallons. For example, a car rated at 30 MPG (US) achieves 30 × 1.20095 = 36.03 MPG (UK). This difference exists because the US gallon is 3.78541 liters while the imperial gallon is 4.54609 liters. When reading fuel economy figures from British publications, always check whether they use imperial or US gallons.

km/L to L/100km

The formula is L/100km = 100 / km/L. Since both metrics use the same base units but in inverse directions, the conversion is simply dividing 100 by the km/L value. For example, a car achieving 15 km/L consumes 100 / 15 = 6.67 L/100km. Conversely, a vehicle rated at 8 L/100km achieves 100 / 8 = 12.5 km/L. This inverse relationship means that improvements at the low-efficiency end of the scale save more fuel in absolute terms than the same numerical improvement at the high-efficiency end.

About the Fuel Economy Converter

Fuel economy measurement varies dramatically around the world, creating confusion for car buyers, travelers, and fleet managers who need to compare vehicles across different markets. The United States uses miles per gallon, most of Europe and Australia use liters per 100 kilometers, and countries like Japan and India use kilometers per liter. This fuel economy converter supports all major standards including both US and UK gallon variants, making cross-market comparison straightforward and accurate.

Understanding Fuel Economy Metrics

The concept of measuring fuel economy emerged alongside the automobile industry in the early 20th century. As cars became mainstream consumer products, buyers needed a way to compare how efficiently different vehicles used fuel. The United States adopted miles per gallon as its standard, a natural choice given that Americans already measured distances in miles and fuel in gallons.

Europe took a different approach. Rather than measuring how far a car can travel on a unit of fuel, the European standard measures how much fuel a car consumes over a fixed distance. Liters per 100 kilometers tells you the cost of driving, making it intuitive for budgeting fuel expenses. A lower L/100km number means better efficiency, which is the opposite of MPG where a higher number is better. This inverse relationship is the single biggest source of confusion when comparing fuel economy across systems.

Japan and several other Asian countries use kilometers per liter, which is conceptually similar to MPG but uses metric units. Like MPG, a higher km/L number indicates better efficiency. India also uses km/L as its primary fuel economy metric, and it appears prominently in car advertisements and government fuel economy ratings in those markets.

The distinction between US and UK MPG is another important nuance. Because the imperial gallon is about 20 percent larger than the US gallon, the same vehicle will always show a higher MPG number when measured in imperial gallons. A car rated at 30 MPG (US) achieves 36 MPG (UK). British and some older Commonwealth publications use imperial MPG, while American sources use US MPG. Failing to distinguish between the two can lead to significant misunderstandings about a vehicle's actual efficiency.

Electric vehicles have introduced yet another metric: miles per gallon equivalent, or MPGe. This standard, defined by the US Environmental Protection Agency, compares the energy content of electricity to that of gasoline. One gallon of gasoline contains approximately 33.7 kilowatt-hours of energy. An electric car that travels 100 miles on 33.7 kWh is rated at 100 MPGe. Most modern electric vehicles achieve between 90 and 140 MPGe, making them significantly more energy-efficient than conventional gasoline cars, though direct cost comparisons depend on local electricity and fuel prices.

Common Fuel Economy Conversions in Daily Life

Car shopping across international markets is one of the most frequent reasons people need a fuel economy converter. An American considering a European import will see efficiency rated in L/100km on the manufacturer's specification sheet. A rating of 5.5 L/100km sounds abstract until you convert it to 42.8 MPG (US), which immediately communicates excellent highway efficiency. Similarly, a Japanese car rated at 20 km/L equals 47.0 MPG (US) or 4.99 L/100km, placing it among the most efficient non-hybrid gasoline vehicles available.

Travel and car rental situations also demand fuel economy conversion. An American renting a car in France will see fuel priced per liter and the car's consumption rated in L/100km. Understanding that 7 L/100km means the car uses about 33.6 MPG (US) helps estimate trip fuel costs. If fuel costs 1.80 euros per liter and you plan to drive 500 km, the car will consume about 35 liters, costing roughly 63 euros. Without converting to familiar units, this kind of budgeting becomes guesswork. For distance conversions during road trips, our length unit converter handles miles-to-kilometers and other distance calculations.

Fleet management and corporate sustainability reporting require standardized fuel economy comparisons. A logistics company operating trucks in both the US and Europe needs to convert between MPG and L/100km to create unified efficiency reports. A truck averaging 8 MPG (US) consumes 29.4 L/100km, while a European counterpart rated at 25 L/100km achieves 9.4 MPG (US). These conversions help identify which vehicles in a mixed fleet are the most and least efficient, guiding replacement and routing decisions.

Comparing hybrid and electric vehicles to conventional cars also requires fuel economy conversion. A hybrid rated at 50 MPG (US) consumes 4.7 L/100km, while a conventional sedan at 30 MPG (US) uses 7.84 L/100km. The hybrid saves about 3.14 liters per 100 km. Over 20,000 km of annual driving, that translates to 628 liters of fuel saved per year. For fuel volume conversions when calculating tank sizes and fill-ups, our volume unit converter provides instant results.

Tips and Quick Reference

A handy shortcut for converting mpg to l/100km: divide 235 by the MPG value. This rounded constant is easy to remember and gives results accurate to within 0.1 percent of the exact factor. For example, 30 MPG is roughly 235 / 30 = 7.83 L/100km, compared to the exact value of 7.84. For mental math at the car dealership, this approximation is more than sufficient.

Remember that L/100km and MPG move in opposite directions. When L/100km goes down, efficiency improves; when MPG goes up, efficiency improves. This inverse relationship also means that the scale is not linear. Improving from 10 to 20 MPG saves far more fuel than improving from 30 to 40 MPG. Going from 10 to 20 MPG cuts fuel consumption in half, while going from 30 to 40 MPG reduces it by only 25 percent. The L/100km metric makes this asymmetry more visible because the numbers change proportionally to actual fuel savings.

A common mistake is confusing US and UK MPG figures. If you see a British car review claiming 50 MPG, that is imperial MPG, which equals only about 41.6 MPG (US) or 5.65 L/100km. Always check the source country before comparing fuel economy numbers. Australian publications use L/100km, Canadian sources may use either L/100km or MPG (imperial), and Japanese sources use km/L. When comparing vehicle speeds across countries, our speed unit converter handles mph-to-kph and other velocity calculations.

Common Fuel Economy Reference Values

The following table lists frequently used fuel economy equivalents for quick lookups. These cover typical vehicle categories and help you understand what different fuel economy ratings mean in practical terms.

Vehicle Type	MPG (US)	MPG (UK)	L/100km	km/L
Large SUV / Truck	15 MPG	18.0 MPG	15.68 L/100km	6.38 km/L
Midsize SUV	22 MPG	26.4 MPG	10.69 L/100km	9.35 km/L
Average sedan	30 MPG	36.0 MPG	7.84 L/100km	12.75 km/L
Efficient compact	38 MPG	45.6 MPG	6.19 L/100km	16.16 km/L
Hybrid sedan	50 MPG	60.0 MPG	4.70 L/100km	21.26 km/L
Plug-in hybrid (gas mode)	42 MPG	50.4 MPG	5.60 L/100km	17.86 km/L
Diesel sedan	40 MPG	48.0 MPG	5.88 L/100km	17.01 km/L
Motorcycle	55 MPG	66.1 MPG	4.28 L/100km	23.38 km/L
Heavy-duty truck	6 MPG	7.2 MPG	39.20 L/100km	2.55 km/L

Frequently Asked Questions

How do I convert MPG to L/100km?

Divide 235.215 by the MPG (US) value. For example, 25 MPG (US) equals 235.215 / 25 = 9.41 L/100km. If you are starting with imperial MPG (UK), divide 282.481 by the MPG value instead. The relationship is inverse, meaning you always divide a constant by the MPG number rather than multiplying. A higher MPG value produces a lower L/100km value, and vice versa. This converter handles both US and imperial MPG automatically.

What is the difference between MPG (US) and MPG (UK)?

MPG (US) uses the US gallon of 3.78541 liters, while MPG (UK) uses the imperial gallon of 4.54609 liters. Because the imperial gallon is about 20 percent larger, the same vehicle always shows a higher number in MPG (UK). To convert from US to UK, multiply by 1.20095. To convert from UK to US, multiply by 0.83267. A car rated at 30 MPG (US) achieves 36.03 MPG (UK). This distinction is critical when reading car reviews from different countries, as confusing the two can lead to a 20 percent error in your fuel cost estimates.

What is MPGe and how does it relate to MPG?

MPGe stands for miles per gallon equivalent, a metric created by the US Environmental Protection Agency to compare the energy efficiency of electric and alternative-fuel vehicles to gasoline cars. One gallon of gasoline contains approximately 33.7 kilowatt-hours of energy. If an electric car can travel 100 miles using 33.7 kWh, it is rated at 100 MPGe. Most modern electric vehicles achieve between 90 and 140 MPGe. However, MPGe does not directly translate to fuel cost savings because electricity prices per kWh vary widely by region and are typically much lower per unit of energy than gasoline.

Why does Europe use L/100km instead of MPG?

Europe adopted liters per 100 kilometers because it directly represents fuel consumption rather than fuel efficiency. This makes it easier to calculate trip costs: multiply L/100km by the distance in hundreds of kilometers, then multiply by the fuel price per liter. The metric also better reflects actual fuel savings. Improving from 10 to 8 L/100km saves 2 liters per 100 km, and improving from 6 to 4 L/100km also saves 2 liters per 100 km. With MPG, the same absolute fuel savings produce different numerical changes, making comparisons less intuitive.

How do I calculate fuel cost for a road trip?

If you know the fuel economy in L/100km, multiply by the trip distance in hundreds of kilometers, then multiply by the fuel price per liter. For example, a 600 km trip in a car that consumes 7 L/100km requires 6 × 7 = 42 liters of fuel. At 1.60 euros per liter, the trip costs 67.20 euros. If you know the fuel economy in MPG, divide the trip distance in miles by the MPG value to get gallons needed, then multiply by the price per gallon. A 400-mile trip at 30 MPG requires 13.33 gallons. At 3.50 dollars per gallon, the trip costs 46.67 dollars.

What is considered good fuel economy?

Good fuel economy depends on the vehicle category. For a compact car, 35 to 40 MPG (US) or 5.9 to 6.7 L/100km is considered good. For a midsize sedan, 28 to 35 MPG (US) or 6.7 to 8.4 L/100km is respectable. SUVs achieving 25 MPG (US) or 9.4 L/100km are above average for their class. Hybrid vehicles typically achieve 45 to 60 MPG (US) or 3.9 to 5.2 L/100km. Full electric vehicles, measured in MPGe, commonly achieve 90 to 140 MPGe. These benchmarks shift over time as engine technology improves and emissions regulations tighten.

How do driving conditions affect fuel economy?

Real-world fuel economy often differs significantly from official ratings. Highway driving at steady speeds typically yields the best fuel economy, while city driving with frequent stops and starts consumes more fuel due to energy lost during braking and idling. Cold weather reduces fuel economy by 10 to 20 percent because engines take longer to reach optimal operating temperature and winter fuel blends contain less energy. Air conditioning can reduce fuel economy by up to 25 percent in extreme heat. Aggressive driving habits like rapid acceleration and hard braking can lower fuel economy by 15 to 30 percent compared to smooth, moderate driving.

How do diesel and gasoline fuel economy compare?

Diesel engines are typically 20 to 35 percent more fuel-efficient than equivalent gasoline engines because diesel fuel contains about 15 percent more energy per liter and diesel engines operate at higher compression ratios, extracting more work from each combustion cycle. A gasoline sedan achieving 30 MPG (US) might have a diesel equivalent rated at 38 to 40 MPG (US). However, diesel fuel often costs more per liter than gasoline, and diesel vehicles may have higher purchase prices and maintenance costs. The total cost of ownership depends on annual mileage, local fuel prices, and the price premium for the diesel variant.

How do I convert km/L to MPG?

Multiply the km/L value by 2.35215 to get MPG (US), or multiply by 2.82481 to get MPG (UK). For example, a car rated at 15 km/L achieves 15 × 2.35215 = 35.28 MPG (US). To go the other direction, divide MPG (US) by 2.35215 or equivalently multiply by 0.425144. The km/L metric is popular in Japan and India, where it appears on vehicle window stickers and in manufacturer specifications. When comparing vehicles across these markets with US or European models, accurate conversion is essential for making informed purchasing decisions.

How accurate is this fuel economy converter?

This converter uses IEEE 754 double-precision floating-point arithmetic, providing approximately 15 to 17 significant decimal digits of precision. The conversion constants are derived from the internationally agreed definitions of the mile, kilometer, US gallon, imperial gallon, and liter as maintained by the National Institute of Standards and Technology and the International Bureau of Weights and Measures. For all practical applications including vehicle comparison, trip planning, and fleet management, the results are effectively exact. All calculations run entirely in your browser using JavaScript.

What fuel economy standards do governments require?

Government fuel economy standards vary by country and are becoming increasingly strict. The United States Corporate Average Fuel Economy (CAFE) standards require automakers to achieve fleet-wide averages that are progressively tightened each model year. The European Union sets CO2 emission targets in grams per kilometer, which correlate directly with fuel consumption in L/100km. China uses a fuel consumption standard measured in L/100km, and Japan uses a km/L-based standard. These regulations drive manufacturers to improve engine efficiency, reduce vehicle weight, and develop hybrid and electric powertrains. Understanding fuel economy conversions helps consumers evaluate whether vehicles meet or exceed their country's standards.

Can I use this converter offline?

Yes. Because all calculations run in your browser using client-side JavaScript, the fuel economy converter works without an internet connection once the page has loaded. No data is transmitted to any server during the conversion process. This makes it ideal for use at car dealerships, during road trips, or in fleet management offices where you need quick conversions between MPG, L/100km, km/L, and other fuel economy units. Simply bookmark this page for instant access anytime you need to compare fuel efficiency across different measurement standards.