MPG to L/100km Converter
How this MPG to L/100km converter works
This calculator lets you convert fuel economy between U.S. miles per gallon (MPG) and liters per 100 kilometers (L/100km). The tool works in both directions: you can start with MPG to find L/100km, or start with L/100km to find the equivalent MPG rating.
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.
Conversion formulas
MPG and L/100km describe the same thing (how much fuel your vehicle uses), but they do it in opposite ways:
- 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.
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 constant comes from
The constant is based on standard 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 real-world conclusions about fuel economy.
Worked example
Imagine you are comparing cars and see one rated at 30 MPG (U.S.). A European brochure for a similar vehicle lists L/100km, and you want to know the equivalent value.
- Start from the MPG-to-L/100km formula: L/100km = 235.214583 ÷ MPG.
- Substitute MPG = 30: L/100km = 235.214583 ÷ 30.
- 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:
- Start from the L/100km-to-MPG formula: MPG = 235.214583 ÷ (L/100km).
- Substitute L/100km = 5.5: MPG = 235.214583 ÷ 5.5.
- Compute the division: 235.214583 ÷ 5.5 ≈ 42.77.
So 5.5 L/100km corresponds to about 42.8 MPG (U.S.).
Quick reference table
The table below shows common fuel economy values converted between U.S. MPG and L/100km so you can quickly compare ratings without doing the math yourself.
| MPG (U.S.) | L/100km |
|---|---|
| 20 | 11.76 |
| 25 | 9.41 |
| 30 | 7.84 |
| 35 | 6.72 |
| 40 | 5.88 |
| 50 | 4.70 |
Notice how as MPG increases, the corresponding L/100km value decreases. Both patterns represent the same idea: 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
The following table summarizes key differences between the two fuel economy measures.
| Aspect | MPG (miles per gallon) | L/100km (liters per 100 km) |
|---|---|---|
| Unit system | Imperial distance and volume (U.S. mile and U.S. gallon) | Metric distance and volume (kilometer and liter) |
| Common regions | United States and some U.S.-focused publications | Most metric-system countries, including much of Europe and Asia-Pacific |
| "Better" direction | Higher MPG is better (more miles per gallon) | Lower L/100km is better (fewer liters per 100 km) |
| Interpretation | Focuses on how far you can go on a fixed amount of fuel | Focuses on how much fuel you need to travel a fixed distance |
| Typical display | Vehicle window stickers and EPA estimates in the U.S. | Official fuel economy labels and brochures in many metric countries |
| Ease of mental math | Intuitive if you think in miles and gallons; harder to compare small differences | Intuitive if you think in liters and kilometers; easier to reason about fuel used per trip |
U.S. gallons vs imperial gallons
This converter is based on U.S. gallons. Some regions, especially the U.K. and older Canadian data, may use imperial gallons, which are larger than U.S. gallons:
- 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:
- Convert imperial MPG to U.S. MPG first using an approximate factor:
U.S. MPG ≈ imperial MPG × 1.20095. - 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 size of the imperial gallon.
Interpreting your results
Once you have converted between MPG and L/100km, you can use the numbers to make more informed decisions about vehicles and driving habits:
- Comparing cars: if one model has higher MPG (or lower L/100km) than another, it should, in principle, use less fuel for the same distance driven.
- Estimating running costs: combining fuel economy with local fuel prices and your typical annual mileage helps you estimate yearly fuel expenses.
- Understanding brochure claims: international brochures or reviews may mix units; converting them to your familiar unit avoids confusion.
- Tracking efficiency changes: if your real-world fuel economy starts to drift significantly from the rated value, it may signal changes in driving style, cargo load, tire pressure, or vehicle maintenance needs.
Remember that official fuel economy ratings are measured under controlled test cycles. Real-world results often differ due to speed, traffic, weather, and driving style.
Assumptions and limitations
This calculator is designed to be straightforward, but it is important to understand what it does and does not account for.
- U.S. gallons only: all conversions are based on U.S. gallons. Imperial gallons require an extra adjustment step as described in the section on U.S. vs imperial gallons.
- Approximate values: the constants used (for miles, kilometers, gallons, and liters) are standard approximations. Small rounding differences may appear, especially when you enter many decimal places, but they are negligible for practical use.
- Theoretical extremes: you can enter very high or very low numbers to see how the formulas behave, but extreme values may not correspond to realistic vehicle performance.
- No driving conditions: the tool converts units only. It does not adjust for traffic, terrain, temperature, driving style, or load. Those factors can significantly affect 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
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 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 these effects; it only changes how the same efficiency is expressed.