How do I convert mpg to L/100km?

Divide 235.21 by the mpg (US) value, or 282.48 by the mpg (UK) value. For example, 30 mpg (US) is about 7.84 L/100km.

Is a higher mpg or a lower L/100km better?

Both describe better fuel economy, but they move in opposite directions: a higher mpg (or km/L) number is better, while a lower L/100km (or L/100mi) number is better, because it measures fuel used rather than distance covered.

What is a good L/100km for a car?

Roughly 5-7 L/100km is efficient for a modern petrol car, 8-10 L/100km is average, and anything above 12 L/100km is considered thirsty. Hybrids and small diesels often achieve 4-5 L/100km.

Why is mpg (US) different from mpg (UK)?

A US gallon (3.785 liters) is smaller than a UK imperial gallon (4.546 liters). For the same car, that makes the mpg (UK) figure about 20% higher than the mpg (US) figure, even though the vehicle's actual efficiency hasn't changed.

How many liters are in a US gallon vs a UK gallon?

A US gallon is 3.785411784 liters. A UK imperial gallon is 4.54609 liters — about 20% more.

How do I calculate how much fuel I need for a trip?

Divide your trip distance by your car's efficiency (in matching units), or use the "Fuel Needed for a Trip" calculator above, which handles the unit conversion automatically.

How do I calculate the cost of fuel for a trip?

Work out the liters needed for the trip, then multiply by your local price per liter. The "Fuel Cost for a Trip" calculator above does both steps at once.

What is km/L and how does it compare to mpg?

Km/L (kilometers per liter) is a metric efficiency unit, directly comparable to mpg in concept — higher is better for both. 1 km/L is about 2.35 mpg (US) or 2.82 mpg (UK).

How accurate are these fuel consumption conversions?

All conversions use exact, internationally defined constants for the US gallon, UK gallon and mile, so the math is precise. Real-world fuel economy still varies with driving style, terrain and vehicle condition.

Can I use this tool for diesel as well as petrol/gasoline?

Yes. The unit conversions are the same regardless of fuel type — only the price you enter in the trip cost calculator needs to match whichever fuel your vehicle uses.

Why does L/100km use "per 100" instead of a simple ratio?

Measuring liters per single kilometer would produce awkward, tiny decimals. Scaling to 100 kilometers keeps the numbers in an easy-to-read range, similar to how percentages scale to 100.

Is this fuel consumption converter free to use?

Yes, it is completely free, requires no registration, and runs entirely in your browser with no usage limits.

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Fuel Conversion

7 units · 4 trip calculators

Fuel Consumption Converter & Trip Calculator

Convert between MPG (US & UK), L/100km, km/L and more, then work out how much fuel a trip will use, what it will cost, or how far you can drive on a full tank — all calculated instantly in your browser.

7Fuel economy units

4Trip calculators

0msServer round-trips

Distance unit Consumption rate unit

32L

Fuel = Distance ÷ Efficiency = 400 km ÷ 12.5 km/L = 32 L

From

mpg (US)

To

L/100km

7.8404861L/100km

L/100km = 235.21 / mpg (US)

Runs locally, no data sent Exact US/UK gallon & mile constants Free, no sign-up

How each calculation works

The formula behind each calculator above, with a short note on when you'd use it.

Quick conversion table

Common values for your selected units in the converter above, updated automatically.

MPG (US)	L/100km

Fuel consumption unit reference

What each unit means, where it's used, and whether a higher or lower number means better fuel economy.

More converters from ConvertGPT

Working across other units too? These are the ones people pair with fuel consumption most often.

Frequently asked questions

Straight answers to the questions people ask most about fuel economy and consumption.

All calculations and conversions run locally in your browser using exact US/UK gallon and mile constants. No data is sent anywhere.

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