⛽ Fuel Economy Converter: MPG, L/100km, km/L and MPG (UK)
By Shihab Mia · Updated 2026-07-16
Remember: higher MPG and km/L are better, while a lower L/100km is better.
Type in any box and the other three update instantly. Values are rounded for display.
Enter any fuel economy figure and this converter instantly shows the other three: MPG (US), MPG (UK), L/100km and km/L. It solves the everyday problem that the same car is quoted differently around the world. The United States uses miles per US gallon, the United Kingdom uses miles per Imperial gallon, most of Europe, Australia and Asia use litres per 100 kilometres, and some regions use kilometres per litre. Type a value into any box, or tap a preset, and compare a spec sheet, a road test or your own fuel log no matter which standard it uses.
What is the Fuel Economy Converter?
Fuel economy is measured two opposite ways, and mixing them up is the single most common error. Distance-per-fuel measures (MPG and km/L) get bigger when a car is more efficient, because you travel further on the same fuel. Fuel-per-distance measures (L/100km) get smaller when a car is more efficient, because you burn less fuel over the same distance. So a high MPG is good, but a high L/100km is bad. The two are inversely related, which is why you cannot simply add or average them across units.
The other trap is the gallon. A US gallon is about 3.785 litres while an Imperial (UK) gallon is about 4.546 litres, roughly 20 percent larger. Because the UK gallon holds more fuel, the same car always scores a higher number in MPG (UK) than in MPG (US). A car rated at 30 MPG (US) is about 36 MPG (UK), even though nothing about the car has changed. Always check which gallon a figure refers to before comparing two vehicles, because a US 40 MPG car and a UK 40 MPG car are not the same car.
This tool converts through a single internal value in L/100km. From any input it works out the litres burned per 100 km, then expresses that same consumption in every other unit. The key relationships are L/100km = 235.215 divided by MPG (US), L/100km = 282.481 divided by MPG (UK), and km/L = MPG (US) multiplied by 0.425144. Because everything routes through one pivot, the conversions stay consistent in both directions and never drift.
Context helps you read the result. The average model year 2024 new vehicle in the United States achieved a record real-world fuel economy of 27.2 MPG (US), which is about 8.65 L/100km, according to the EPA Automotive Trends Report. As a rough guide, a frugal petrol family car sits under about 7.0 L/100km (over 33.6 MPG US or 40.3 MPG UK), while full hybrids often reach 4.5 to 5.5 L/100km (43 to 52 MPG US). Diesels and small city cars can do better still. Anything much above 12 L/100km (under about 20 MPG US) is thirsty by modern standards.
Official ratings and real driving rarely match. The United States quotes EPA figures, while Europe and much of the world now use the WLTP test (Worldwide Harmonised Light Vehicles Test Procedure). The two labs use different cycles, so a US EPA 30 MPG and a European WLTP 7.8 L/100km can describe the same car yet neither is what you will see on the road. Real-world consumption is commonly 10 to 20 percent worse than the sticker because of aggressive driving, air conditioning, cold starts, roof racks and short trips. Convert the official number here, then add a margin for how and where you actually drive.
Electric cars are measured on a separate scale, MPGe (miles per gallon equivalent), where the EPA treats 33.7 kilowatt-hours of electricity as the energy in one US gallon of petrol. Because an EV burns no liquid fuel, MPGe and km/L are not directly comparable to petrol figures and this converter deliberately covers only the four liquid-fuel units. If you are comparing an EV, use its MPGe and cost-per-mile instead of trying to force it onto an MPG or L/100km scale.
When to use it
- Comparing a US car spec quoted in MPG (US) with a European model quoted in L/100km.
- Converting a fuel log kept in km/L into MPG to check it against a manufacturer rating.
- Translating a UK road-test MPG (UK) figure into MPG (US) before buying an imported vehicle.
- Working out the L/100km a rental car will use when you are travelling abroad and budgeting fuel.
- Checking whether a quoted economy figure uses the US gallon or the larger Imperial gallon.
- Sanity-checking a car listing by converting the claimed figure into the unit you know best.
How to use the Fuel Economy Converter
- Pick the unit you already have a number for (MPG US, MPG UK, L/100km, or km/L).
- Type that value into its box, or tap one of the MPG (US) preset buttons.
- Read the other three boxes, which fill in automatically as you type.
- Check the summary line, which restates all four values together for easy comparison.
- Remember to add roughly 10 to 20 percent for real-world driving if you started from an official rating.
Formula & method
Worked examples
A US car is rated at 30 MPG (US) and you want the European equivalent in L/100km and km/L.
- Convert to L/100km: 235.215 / 30 = 7.8405, so about 7.84 L/100km.
- Convert to km/L: 30 x 0.425144 = 12.7543, so about 12.75 km/L.
- Convert to MPG (UK): 30 x 1.20095 = 36.0285, so about 36.03 MPG (UK).
Result: 30 MPG (US) is about 7.84 L/100km, 12.75 km/L, and 36.03 MPG (UK).
A European hatchback is listed at 6 L/100km and you want to compare it against US figures.
- Convert to MPG (US): 235.215 / 6 = 39.2025, so about 39.20 MPG (US).
- Convert to MPG (UK): 282.481 / 6 = 47.0802, so about 47.08 MPG (UK).
- Convert to km/L: 100 / 6 = 16.6667, so about 16.67 km/L.
Result: 6 L/100km is about 39.20 MPG (US), 47.08 MPG (UK), and 16.67 km/L.
A UK review quotes 50 MPG (UK) and you want the true US MPG and metric figures.
- Convert to MPG (US): 50 / 1.20095 = 41.6337, so about 41.63 MPG (US).
- Convert to L/100km: 282.481 / 50 = 5.6496, so about 5.65 L/100km.
- Convert to km/L: 100 / 5.6496 = 17.7005, so about 17.70 km/L.
Result: 50 MPG (UK) is only about 41.63 MPG (US), or 5.65 L/100km and 17.70 km/L, so the UK figure looks better than it really is.
Common fuel economy values across all four units
| MPG (US) | MPG (UK) | L/100km | km/L |
|---|---|---|---|
| 20 | 24.02 | 11.76 | 8.50 |
| 25 | 30.02 | 9.41 | 10.63 |
| 30 | 36.03 | 7.84 | 12.75 |
| 40 | 48.04 | 5.88 | 17.01 |
| 50 | 60.05 | 4.70 | 21.26 |
| 60 | 72.06 | 3.92 | 25.51 |
What counts as good economy, by vehicle type (approximate)
| Vehicle type | Typical L/100km | Roughly MPG (US) |
|---|---|---|
| Small city car (petrol) | 5.0 to 6.5 | 36 to 47 |
| Family sedan (petrol) | 6.5 to 8.5 | 28 to 36 |
| Full hybrid | 4.0 to 5.5 | 43 to 59 |
| Small or mid SUV | 7.5 to 10.0 | 24 to 31 |
| Large SUV or pickup | 10.0 to 14.0 | 17 to 24 |
| Average new US vehicle (MY2024) | about 8.65 | about 27.2 |
Conversion factors used by this tool
| From | To | Operation |
|---|---|---|
| MPG (US) | L/100km | divide 235.215 by the MPG value |
| MPG (UK) | L/100km | divide 282.481 by the MPG value |
| MPG (US) | km/L | multiply by 0.425144 |
| MPG (US) | MPG (UK) | multiply by 1.20095 |
| L/100km | km/L | divide 100 by the L/100km value |
Common mistakes to avoid
- Treating MPG and L/100km as if they move the same way. They are inverse measures. A higher MPG means better economy, but a higher L/100km means worse economy. Improving from 8 to 6 L/100km is a gain, not a loss.
- Confusing US gallons with Imperial gallons. The Imperial gallon is about 20 percent larger than the US gallon, so MPG (UK) always reads higher than MPG (US) for the same car. Mixing them makes a vehicle look more efficient than it is.
- Averaging fuel economy across a trip. You cannot simply average two MPG figures to get a trip average, because economy is fuel per distance. Add up the total distance and the total fuel, then divide, or convert to L/100km first.
- Assuming km/L and L/100km are interchangeable units. Both are metric, but one is distance per fuel and the other fuel per distance. Use km/L = 100 divided by L/100km to switch between them rather than guessing.
- Expecting the official rating on the road. EPA and WLTP figures come from a lab. Real driving is usually 10 to 20 percent worse because of air conditioning, cold starts, traffic and driving style. Add a margin before you budget fuel.
- Comparing an EV MPGe against a petrol MPG. MPGe converts electricity to a petrol-energy equivalent (33.7 kWh per gallon) and does not represent liquid fuel. Do not drop an EV MPGe number into an MPG or L/100km comparison.
Glossary
- MPG (US)
- Miles travelled per US gallon (about 3.785 litres) of fuel. Higher is more efficient.
- MPG (UK)
- Miles travelled per Imperial gallon (about 4.546 litres) of fuel, used in the United Kingdom. Higher is more efficient.
- L/100km
- Litres of fuel consumed per 100 kilometres travelled. Lower is more efficient.
- km/L
- Kilometres travelled per litre of fuel, used in parts of Asia. Higher is more efficient.
- Imperial gallon
- The UK gallon, about 4.546 litres, roughly 20 percent larger than the US gallon.
- Inverse relationship
- A link where one value rises as the other falls, as between L/100km and MPG.
- MPGe
- Miles per gallon equivalent, the EPA scale for electric cars, treating 33.7 kWh of electricity as one gallon of petrol.
- WLTP
- Worldwide Harmonised Light Vehicles Test Procedure, the lab test used in Europe and much of the world, distinct from the US EPA test.
Frequently asked questions
How do I convert MPG (US) to L/100km?
Divide 235.215 by the MPG value. For example, 30 MPG (US) equals 235.215 divided by 30, which is about 7.84 L/100km. The conversion is inverse, so a higher MPG always gives a lower L/100km.
How do I convert L/100km to MPG?
For US MPG, divide 235.215 by the L/100km value; for UK MPG, divide 282.481 by it. For example, 8 L/100km equals 235.215 / 8 = about 29.40 MPG (US) or 282.481 / 8 = about 35.31 MPG (UK).
Why is MPG (UK) a bigger number than MPG (US) for the same car?
The Imperial gallon used in the UK holds about 4.546 litres while the US gallon holds about 3.785 litres. Because the UK gallon is roughly 20 percent larger, the car travels more miles on one gallon, so the MPG (UK) figure is higher even though the car is identical.
How do I convert L/100km to km/L?
Divide 100 by the L/100km value. For example, 8 L/100km equals 100 divided by 8, which is 12.5 km/L. They are inverse measures of the same consumption, so as one rises the other falls.
Is a higher or lower number better for fuel economy?
It depends on the unit. For MPG (US), MPG (UK) and km/L, higher is better because you travel further on the same fuel. For L/100km, lower is better because you burn less fuel over the same distance.
What is a good fuel economy figure?
As a rough guide, under about 7.0 L/100km (over 33.6 MPG US) is good for a petrol family car, and full hybrids often reach 4.5 to 5.5 L/100km. For context, the average new US vehicle in model year 2024 managed about 27.2 MPG (US), or 8.65 L/100km.
Why does my car use more fuel than its official rating?
Official EPA and WLTP figures come from a controlled lab test. Real-world driving is typically 10 to 20 percent worse because of aggressive acceleration, air conditioning, cold starts, short trips and traffic. Convert the sticker figure here, then add a margin.
What is the difference between km/L and L/100km?
Both are metric, but km/L is distance per fuel (higher is better) while L/100km is fuel per distance (lower is better). They describe the same efficiency from opposite directions, linked by km/L = 100 divided by L/100km.
Can this converter handle electric cars or MPGe?
No. This tool covers the four liquid-fuel units. Electric cars use MPGe, which converts electricity to a petrol-energy equivalent (33.7 kWh per gallon), so it is not directly comparable to MPG or L/100km. Use an EV cost-per-mile or MPGe figure instead.
How accurate are these conversions?
The conversion factors are exact to the values shown (235.215 for MPG US and 282.481 for MPG UK), so the math is precise. Displayed results are rounded to two decimals for readability, which is plenty for comparing vehicles.
Sources
- The 2025 EPA Automotive Trends Report (average new vehicle 27.2 MPG, MY2024) , U.S. Environmental Protection Agency (2025)
- Fuel economy in automobiles (units, WLTP and EPA test standards) , Wikipedia