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Fuel Consumption Calculator: Convert MPG, L/100km, km/L and More

Fuel economy is expressed differently around the world. A vehicle might be rated at 30 miles per gallon in the United States, 7.8 liters per 100 kilometers in Europe, or 12.8 kilometers per liter in another market. These numbers can describe similar fuel efficiency, but the different units make comparisons difficult.

The CalculatorKits Fuel Consumption Calculator makes those comparisons much easier. You can convert between L/100km, MPG, km/L, mi/L, L/km, gal/100mi, and other fuel consumption units without calculating the formulas manually.

The tool supports 14 fuel consumption units and uses meters per liter as its internal base unit. For example, 10 L/100km converts to approximately 23.5215 US mpg. (calculatorkits.com)

Quick Answer

Here are some of the most common fuel consumption conversions:

Fuel consumption	Equivalent
1 L/100km	2.35215 US mpg
5 L/100km	47.0430 US mpg
8 L/100km	29.4019 US mpg
10 L/100km	23.5215 US mpg
12 L/100km	19.6013 US mpg
15 L/100km	15.6809 US mpg
20 L/100km	11.7608 US mpg
1 US mpg	0.425144 km/L
10 km/L	23.5215 US mpg
15 km/L	35.2823 US mpg
20 km/L	47.0430 US mpg
30 US mpg	7.8405 L/100km

The key formula for US fuel economy is:

US MPG = 235.215 ÷ L/100km

NIST gives the corresponding relationship as dividing 235.215 by the miles per gallon value when converting US mpg to L/100km. (nist.gov)

What Is a Fuel Consumption Calculator?

A Fuel Consumption Calculator converts measurements that describe how efficiently a vehicle uses fuel.

There are two main ways fuel economy is expressed.

Fuel economy tells you how far a vehicle travels per amount of fuel.

Examples include:

Miles per gallon (MPG)

Kilometers per liter (km/L)

Miles per liter (mi/L)

Fuel consumption tells you how much fuel is required to travel a fixed distance.

The most common example is:

Liters per 100 kilometers (L/100km)

This difference is important because the direction of the numbers is reversed.

With MPG and km/L:

Higher number = better efficiency

With L/100km:

Lower number = better efficiency

That is why converting between these measurements can feel unintuitive.

Use the CalculatorKits Fuel Consumption Calculator

The easiest way to convert fuel economy is to use the CalculatorKits Fuel Consumption Calculator.

The tool provides a From and To conversion workflow and supports common measurements such as L/100km, MPG, km/L, mi/L, L/km, and gal/100mi. It also includes quick conversion presets for frequently used combinations. (calculatorkits.com)

How to Use the Calculator

1. Enter the fuel consumption or fuel economy value.
2. Choose the original unit.
3. Select the target unit.
4. View the converted result.
5. Copy the result if you need to use it elsewhere.

For example, suppose a vehicle is rated at:

10 L/100km

Select L/100km as the starting unit and MPG as the target unit.

The result is approximately:

23.5215 US mpg

The calculator handles the conversion automatically.

Why Fuel Consumption Conversion Is Different

Fuel consumption conversion is slightly different from ordinary unit conversion because some fuel economy units are reciprocals of each other.

For example:

10 km/L

means the vehicle travels 10 kilometers using one liter of fuel.

But:

10 L/100km

means the vehicle uses 10 liters to travel 100 kilometers.

These numbers cannot simply be multiplied by the same factor in both directions.

For L/100km and km/L:

km/L = 100 ÷ L/100km

and:

L/100km = 100 ÷ km/L

For example:

100 ÷ 10 = 10 km/L

Therefore:

10 L/100km = 10 km/L

This reciprocal relationship is one of the most important things to understand about fuel economy.

L/100km to MPG

Converting L/100km to US MPG is one of the most common fuel economy calculations.

The formula is:

US MPG = 235.215 ÷ L/100km

For example, if a vehicle consumes 10 L/100km:

235.215 ÷ 10 = 23.5215 mpg

Therefore:

10 L/100km = 23.5215 US mpg

NIST provides the same 235.215 relationship for converting between US miles per gallon and liters per 100 kilometers. (nist.gov)

Common L/100km to US MPG Conversions

L/100km	US MPG
3	78.4050
4	58.8038
5	47.0430
6	39.2025
7	33.6021
8	29.4019
9	26.1350
10	23.5215
12	19.6013
15	15.6809
20	11.7608
25	9.4086

A smaller L/100km value corresponds to a larger MPG value.

MPG to L/100km

To convert US MPG to L/100km:

L/100km = 235.215 ÷ US MPG

For example:

235.215 ÷ 30 = 7.8405 L/100km

Therefore:

30 US mpg = 7.8405 L/100km

Common US MPG to L/100km Conversions

US MPG	L/100km
10	23.5215
15	15.6810
20	11.7608
25	9.4086
30	7.8405
35	6.7204
40	5.8804
45	5.2270
50	4.7043
60	3.9203

Notice the inverse relationship. A car with 40 MPG consumes fewer liters per 100 km than a car with 20 MPG.

km/L to L/100km

This conversion is particularly useful when comparing vehicle specifications from countries that use different conventions.

The formula is:

L/100km = 100 ÷ km/L

For example:

100 ÷ 15 = 6.6667 L/100km

Therefore:

15 km/L = 6.6667 L/100km

Common km/L Conversions

km/L	L/100km
5	20
8	12.5
10	10
12	8.3333
15	6.6667
18	5.5556
20	5
25	4
30	3.3333

This is one of the simplest fuel consumption conversions because the distance basis is already kilometers.

L/100km to km/L

The reverse formula is:

km/L = 100 ÷ L/100km

For example:

100 ÷ 8 = 12.5 km/L

Therefore:

8 L/100km = 12.5 km/L

Another example:

100 ÷ 5 = 20 km/L

So:

5 L/100km = 20 km/L

MPG to km/L

For US MPG:

km/L = MPG × 0.425144

For example:

30 × 0.425144 = 12.7543 km/L

Therefore:

30 US mpg ≈ 12.7543 km/L

NIST lists the US mpg conversion factor to km/L as approximately 0.4251437. (nist.gov)

Common MPG to km/L Conversions

US MPG	km/L
10	4.2514
15	6.3772
20	8.5029
25	10.6286
30	12.7543
35	14.8800
40	17.0057
50	21.2572
60	25.5086

km/L to MPG

The reverse formula is:

US MPG = km/L ÷ 0.425144

or approximately:

US MPG = km/L × 2.35215

For example:

15 km/L × 2.35215 = 35.2823 mpg

Therefore:

15 km/L ≈ 35.28 US mpg

US MPG vs UK MPG

One of the most important fuel economy distinctions is the difference between US gallons and UK Imperial gallons.

A US gallon is smaller than an Imperial gallon.

Because the gallon sizes are different, 30 US mpg is not equal to 30 UK mpg in terms of fuel efficiency.

The approximate relationship is:

1 US mpg = 0.832674 UK mpg

And:

1 UK mpg = 1.20095 US mpg

For example:

30 US mpg ≈ 24.98 UK mpg

while:

30 UK mpg ≈ 36.03 US mpg

This difference can produce a significant error when comparing vehicle specifications from the United States and the United Kingdom.

Always check whether the MPG figure is based on the US gallon or Imperial gallon.

US MPG vs Imperial MPG in L/100km

The conversion constants are different for US and Imperial MPG.

For US MPG:

L/100km = 235.215 ÷ US MPG

For Imperial MPG:

L/100km = 282.481 ÷ Imperial MPG

For example, 30 MPG gives:

US MPG:

235.215 ÷ 30 = 7.8405 L/100km

UK MPG:

282.481 ÷ 30 = 9.4160 L/100km

So simply seeing “30 MPG” is not enough. You need to know which gallon definition is being used.

Why US and UK MPG Are Different

The difference comes from the size of the gallon.

A US liquid gallon is approximately:

3.78541 liters

An Imperial gallon is approximately:

4.54609 liters

The Imperial gallon is therefore significantly larger.

Since MPG measures distance traveled per gallon, a vehicle can appear to have a different MPG figure even though its underlying fuel consumption is the same.

This is why international vehicle comparisons should always identify the MPG standard being used.

Fuel Consumption Conversion Formula

The CalculatorKits tool uses meters per liter as its internal base unit.

The general conversion method is:

Result = (Input × From Factor) ÷ To Factor

For example, the CalculatorKits page shows that:

1 L/100km = 100 m/L

Therefore:

10 L/100km = 1,000 m/L

The converter then changes that base value into the selected target unit. (calculatorkits.com)

This approach gives the calculator one consistent internal reference instead of requiring a separate direct formula for every possible pair of units.

Fuel Consumption Conversion Table

Here is a practical reference for common fuel economy values.

L/100km	km/L	US MPG
3	33.3333	78.4050
4	25	58.8038
5	20	47.0430
6	16.6667	39.2025
7	14.2857	33.6021
8	12.5	29.4019
9	11.1111	26.1350
10	10	23.5215
12	8.3333	19.6013
15	6.6667	15.6809
20	5	11.7608
25	4	9.4086

The values are based on standard fuel economy conversion relationships. (nist.gov)

How to Compare Vehicle Fuel Efficiency

Suppose you are comparing two vehicles.

Vehicle A:

7 L/100km

Vehicle B:

10 L/100km

At first glance, the larger number might appear better. It is not.

Because L/100km measures fuel consumed per fixed distance, the lower number represents better efficiency.

Vehicle A uses less fuel to travel 100 kilometers.

Vehicle A can also be converted to approximately:

33.60 US mpg

Vehicle B:

23.52 US mpg

Now the comparison looks reversed because MPG measures distance traveled per fixed amount of fuel.

This is a useful rule:

Higher MPG = better efficiency

Higher km/L = better efficiency

Lower L/100km = better efficiency

Fuel Consumption vs Fuel Economy

These terms are related but are not exactly the same way of expressing efficiency.

Fuel economy describes distance per unit of fuel:

km/L

MPG

Fuel consumption describes fuel used per unit of distance:

L/100km

For example:

20 km/L

means the vehicle travels 20 kilometers using one liter.

Meanwhile:

5 L/100km

means the vehicle uses 5 liters to travel 100 kilometers.

They describe the same underlying efficiency:

20 km/L = 5 L/100km

The numbers look very different because one is the reciprocal form of the other.

Fuel Consumption and Trip Planning

Fuel consumption conversion becomes particularly useful when planning a long trip.

Suppose your vehicle is rated at:

8 L/100km

and you plan to travel:

500 km

Estimated fuel consumption is:

500 ÷ 100 × 8 = 40 liters

So the trip would require approximately:

40 liters of fuel

If you also need to estimate the money required for the trip, the CalculatorKits Fuel Cost Calculator can combine distance, fuel efficiency, and fuel price to estimate the total trip cost.

Estimating Fuel Used From L/100km

The basic formula is:

Fuel Used = Distance ÷ 100 × L/100km

For example, if a vehicle consumes 6 L/100km and travels 800 km:

800 ÷ 100 × 6 = 48 liters

So approximately 48 liters of fuel would be required under the assumed consumption rate.

Actual fuel use can differ because real driving conditions are not constant.

Traffic, road gradients, weather, speed, tire pressure, vehicle load, and driving style can all affect actual consumption.

Estimating Fuel Used From MPG

When MPG is used, the calculation works in the opposite direction.

For US MPG:

Fuel Used in gallons = Distance in miles ÷ MPG

For example, a vehicle achieving 30 US MPG traveling 300 miles would require:

300 ÷ 30 = 10 gallons

If the fuel price were $4 per gallon, the estimated fuel cost would be:

10 × $4 = $40

For a complete trip cost calculation, use a dedicated fuel cost calculator because fuel price and distance are separate inputs from the conversion itself.

Why Your Real Fuel Economy May Differ

A fuel consumption conversion gives you a mathematical equivalent. It does not guarantee that your vehicle will achieve that exact figure on the road.

Real fuel consumption can change because of:

1. Traffic congestion
2. Frequent acceleration and braking
3. Highway versus city driving
4. Vehicle weight
5. Tire pressure
6. Weather conditions
7. Road gradient
8. Vehicle maintenance
9. Driving speed
10. Air conditioning and other loads

For this reason, a manufacturer rating and your personal fuel economy may not match exactly.

The converter changes units. It does not change the underlying measurement or predict future vehicle performance.

Common Fuel Consumption Mistakes

1. Treating L/100km like MPG

This is the biggest conceptual mistake.

With MPG:

Higher is generally better

With L/100km:

Lower is generally better

2. Multiplying when you should divide

The relationship between L/100km and km/L is reciprocal.

Use:

km/L = 100 ÷ L/100km

not multiplication.

3. Forgetting US versus UK gallons

30 US MPG and 30 UK MPG do not represent the same fuel economy.

Always identify the gallon standard.

4. Confusing MPG with miles

MPG means miles per gallon.

It measures fuel economy, not distance.

5. Mixing liters and gallons

Do not combine a fuel consumption value expressed using liters with a fuel price expressed per gallon unless you first convert the units consistently.

6. Rounding too early

If you are using a conversion as part of a larger calculation, keep additional decimal places until the final step.

7. Assuming converted fuel economy equals real world performance

Conversion changes the unit. It does not account for actual driving conditions.

How Accurate Is the CalculatorKits Fuel Consumption Calculator?

The CalculatorKits tool states that it uses standardized conversion constants and performs calculations using IEEE 754 floating point arithmetic. It also states that rounding is applied for the displayed result rather than being used as an early conversion shortcut. (calculatorkits.com)

For normal vehicle comparisons, travel planning, education, and everyday fuel economy calculations, this provides a practical level of precision.

For certified testing, regulatory reporting, or other applications where measurement standards are legally important, use the applicable official testing procedure rather than relying only on a unit conversion.

NIST publishes the recognized relationship between US MPG and L/100km and identifies 235.215 as the conversion constant for that relationship. (nist.gov)

Who Can Use a Fuel Consumption Calculator?

A fuel consumption converter can be useful for:

1. Drivers comparing vehicle mileage.
2. People importing or researching vehicles from another country.
3. Travelers planning long road trips.
4. Automotive students and technicians.
5. Fleet managers comparing vehicle efficiency.
6. Researchers working with transportation data.
7. Buyers comparing international vehicle specifications.
8. Anyone converting MPG into L/100km or km/L.

It is especially useful when a vehicle specification is published in a unit you do not normally use.

Four Related CalculatorKits Tools

If you are working with fuel economy and travel calculations, these four CalculatorKits tools are useful companions:

1. Fuel Cost Calculator for estimating the fuel expense of a trip using distance, efficiency, and fuel price.
2. Speed Converter for converting km/h, mph, m/s, knots, and other speed measurements.
3. Length Converter for converting kilometers, miles, meters, feet, and other distance units.
4. Energy Converter for converting joules, kilowatt hours, calories, BTU, and other energy units.

Frequently Asked Questions

How do I convert L/100km to MPG?

For US MPG, use:

MPG = 235.215 ÷ L/100km

For example:

235.215 ÷ 8 = 29.4019 MPG

Therefore:

8 L/100km ≈ 29.40 US MPG

How do I convert MPG to L/100km?

For US MPG:

L/100km = 235.215 ÷ MPG

For example:

235.215 ÷ 30 = 7.8405 L/100km

What is 30 MPG in L/100km?

If the figure is 30 US MPG:

30 MPG ≈ 7.8405 L/100km

If it is 30 UK Imperial MPG:

30 MPG ≈ 9.4160 L/100km

The result depends on which gallon definition is being used.

What is 10 L/100km in MPG?

10 L/100km ≈ 23.5215 US MPG

For everyday use, this can be rounded to approximately 23.52 MPG.

What is 20 km/L in MPG?

20 km/L ≈ 47.043 US MPG

What is 15 km/L in L/100km?

Use:

100 ÷ 15 = 6.6667

Therefore:

15 km/L ≈ 6.67 L/100km

Is higher MPG better?

Yes. Higher MPG means the vehicle can travel farther using the same amount of fuel.

Is lower L/100km better?

Yes. Lower L/100km means less fuel is required to travel 100 kilometers.

What is the difference between US MPG and UK MPG?

US MPG uses the US liquid gallon, while UK MPG uses the larger Imperial gallon.

Because the gallons have different volumes, the same numerical MPG value does not represent the same fuel economy.

What is the difference between km/L and L/100km?

They are reciprocal ways of describing fuel efficiency.

For example:

10 km/L = 10 L/100km

20 km/L = 5 L/100km

Is fuel consumption the same as mileage?

Not always in everyday language.

Mileage can refer to how far a vehicle travels per unit of fuel, such as MPG or km/L. Fuel consumption often refers to fuel required for a fixed distance, such as L/100km.

Can I use this calculator for motorcycles?

Yes. The unit conversion itself does not depend on whether the vehicle is a car, motorcycle, truck, or another fuel powered vehicle.

Can I convert fuel consumption without knowing fuel price?

Yes.

Fuel consumption conversion only requires the fuel economy value and the relevant units.

Fuel price is needed only when calculating the monetary cost of fuel.

Does the CalculatorKits Fuel Consumption Calculator store my inputs?

The CalculatorKits page states that calculations are performed locally in the browser and that no personal information or conversion data is stored or shared. (calculatorkits.com)

Is the Fuel Consumption Calculator free?

Yes. The CalculatorKits Fuel Consumption Calculator is available for free online use and does not require registration. (calculatorkits.com)

Key Takeaways

Fuel consumption conversion can be confusing because different countries use different ways to express vehicle efficiency.

The most important relationships are:

US MPG = 235.215 ÷ L/100km

L/100km = 235.215 ÷ US MPG

km/L = 100 ÷ L/100km

L/100km = 100 ÷ km/L

US MPG = km/L × 2.35215

km/L = US MPG × 0.425144

Remember that US MPG and UK Imperial MPG are different because the gallon sizes are different.

Also remember the direction of the measurement:

Higher MPG = better fuel economy

Higher km/L = better fuel economy

Lower L/100km = better fuel economy

For quick and reliable conversions, the CalculatorKits Fuel Consumption Calculator lets you convert between multiple fuel consumption units without performing the reciprocal calculations yourself.

When comparing vehicles internationally, always check the unit definition before comparing the numbers. A seemingly better MPG figure may simply be using a different gallon standard.

References

1. NIST Guide to the SI, Appendix B: Conversion Factors
2. NIST Guide to the SI, Appendix B.9: Factors for Units by Quantity
3. NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically

Written and reviewed by the CalculatorKits Editorial Team
Last Updated: September 10, 2026