MPG to L/100km Converter

How this MPG to L/100km converter reads your input

This MPG to L/100km converter translates fuel economy between U.S. miles per gallon (MPG) and liters per 100 kilometers (L/100km), so you can work in whichever unit appears on the label, brochure, or dashboard you are comparing.

To use it, enter a value in either the MPG field or the L/100km field and leave the other box empty. Then run the conversion to see the matching fuel efficiency in the other unit.

MPG to L/100km conversion formulas

MPG and L/100km are two ways of describing the same fuel economy measurement, but they emphasize opposite directions: one counts distance per fuel, the other counts fuel per distance.

• MPG (miles per gallon) – higher numbers mean better fuel economy.
• L/100km (liters per 100 kilometers) – lower numbers mean better fuel economy.

Because of this, the relationship between MPG and L/100km is inverse: as one goes up, the other goes down for the same vehicle.

Using U.S. miles and U.S. gallons, the standard conversion constant is about 235.214583. The core formulas are:

From MPG to L/100km

L/100km = 235.214583 ÷ MPG

From L/100km to MPG

MPG = 235.214583 ÷ (L/100km)

The same relationship can be expressed in MathML as:

If you solve the same equation for MPG instead, you get:

Where the 235.214583 MPG conversion constant comes from

The constant behind MPG to L/100km conversion comes directly from standard U.S. and metric unit definitions.

• 1 U.S. mile = 1.60934 kilometers
• 1 U.S. gallon = 3.78541 liters

Conceptually, if a vehicle drives 1 mile on 1 gallon, that is 1 MPG. To express the same efficiency as liters per 100 kilometers, you convert both the distance and the fuel volume into metric units, then scale to 100 km. Doing the algebra produces:

235.214583 ≈ (100 × 3.78541) ÷ 1.60934

The calculator may round this constant slightly for practical use, but any rounding is small enough that it will not change the fuel-economy comparison in ordinary driving.

Worked example: converting 30 MPG to L/100km

Here is a concrete MPG to L/100km example using a familiar U.S. fuel economy rating of 30 MPG (U.S.).

1. Start from the MPG-to-L/100km formula: L/100km = 235.214583 ÷ MPG.
2. Substitute MPG = 30: L/100km = 235.214583 ÷ 30.
3. Compute the division: 235.214583 ÷ 30 ≈ 7.84.

So a fuel economy of 30 MPG (U.S.) is roughly 7.84 L/100km.

Going the other way, suppose a spec sheet shows 5.5 L/100km and you want U.S. MPG:

1. Start from the L/100km-to-MPG formula: MPG = 235.214583 ÷ (L/100km).
2. Substitute L/100km = 5.5: MPG = 235.214583 ÷ 5.5.
3. Compute the division: 235.214583 ÷ 5.5 ≈ 42.77.

So 5.5 L/100km corresponds to about 42.8 MPG (U.S.).

MPG to L/100km quick reference table

This MPG to L/100km quick reference table shows common fuel economy values in both units so you can compare ratings without recalculating each time.

Notice how as MPG increases, the corresponding L/100km value decreases. Both patterns represent the same fuel economy: higher MPG and lower L/100km both mean you are using less fuel to travel the same distance.

MPG vs L/100km at a glance for fuel economy comparisons

This MPG vs L/100km comparison table highlights how the two units describe the same driving efficiency from opposite angles.

U.S. gallons vs imperial gallons in MPG conversion

This MPG to L/100km converter is based on U.S. gallons, which matters because imperial MPG uses a different gallon size.

• 1 imperial gallon ≈ 4.54609 liters
• 1 U.S. gallon ≈ 3.78541 liters

If you have an MPG value that you know is based on imperial gallons and want to compare it with U.S. MPG or L/100km, there are two approaches:

1. Convert imperial MPG to U.S. MPG first using an approximate factor:
   U.S. MPG ≈ imperial MPG × 1.20095.
2. Then use the standard formulas on this page to convert that U.S. MPG value to L/100km.

When you work entirely in imperial units, the corresponding constant is about 282.481 instead of 235.214583. That difference reflects the larger imperial gallon.

Interpreting your MPG to L/100km results

Once you have converted between MPG and L/100km, you can use the result to compare vehicles, estimate fuel costs, and spot changes in real-world efficiency.

• Comparing cars: if one model has higher MPG or lower L/100km than another, it should use less fuel to cover the same distance.
• Estimating running costs: pairing the converted fuel economy with local fuel prices and your annual mileage can help you estimate yearly fuel expenses.
• Understanding brochure claims: international brochures or reviews may mix MPG and L/100km, so converting them to the unit you know prevents apples-to-oranges comparisons.
• Tracking efficiency changes: if your real-world fuel economy drifts away from the rated value, the gap may point to driving style, cargo load, tire pressure, maintenance, or seasonal conditions.

Remember that official fuel economy ratings are measured under controlled test cycles. Real-world MPG and L/100km values often differ because speed, traffic, weather, and driving style all affect fuel use.

Assumptions and limitations for this MPG to L/100km converter

This MPG to L/100km converter is straightforward, but it only handles the unit change itself and does not model every factor that affects fuel use.

• U.S. gallons only: all conversions are based on U.S. gallons. Imperial gallons require the extra adjustment described above.
• Approximate values: the constants used for miles, kilometers, gallons, and liters are standard approximations. Small rounding differences may appear at many decimal places, but they are negligible for everyday comparison.
• Theoretical extremes: you can enter very high or very low numbers to see how the formulas behave, but extreme results may not describe a realistic vehicle.
• No driving conditions: the tool converts units only. It does not adjust for traffic, terrain, temperature, driving style, or load, all of which can change real-world fuel consumption.
• No specific vehicle modeling: the calculator does not model engines, aerodynamics, or hybrid systems. It only translates fuel economy from one unit system to another.

Frequently asked questions about MPG to L/100km conversions

Is higher MPG or lower L/100km better?

Higher MPG is better because it means you travel more miles on each gallon of fuel. Lower L/100km is better because it means you use fewer liters of fuel to drive 100 kilometers. When you convert between them, a high MPG number will always correspond to a low L/100km number for the same vehicle.

Does this converter use U.S. or imperial gallons?

The converter uses U.S. gallons. If your data is in imperial MPG, convert it to U.S. MPG first (approximately multiply by 1.20095) before using this tool, or use the imperial-specific constant of about 282.481 if you are doing the math manually.

How accurate are the MPG to L/100km conversions?

The conversions are mathematically precise within normal rounding limits. Any small differences from other sources usually come from slightly different rounding of constants or from rounding MPG and L/100km to a limited number of decimal places.

Why do real-world fuel economy numbers differ from official ratings?

Official test procedures are standardized, but everyday driving is not. Heavy traffic, high speeds, frequent acceleration, cold weather, roof racks, and underinflated tires can all reduce real-world fuel economy. Unit conversion does not change those effects; it only changes how the same efficiency is expressed.