Fuel Economy Conversion Table – MPG, L/100 km & km/L
Convert common car fuel economy figures between litres per 100 kilometres, kilometres per litre, US miles per gallon and UK Imperial miles per gallon.
L/100 km to MPG and km/L conversion table
Find the metric consumption figure in the first column, then read across. For L/100 km, a lower number means less fuel is used. For MPG and km/L, a higher number means the car travels farther on the same fuel volume.
| L/100 km | US MPG | UK MPG | km/L |
|---|---|---|---|
| 2.0 | 117.6 | 141.2 | 50.0 |
| 2.5 | 94.1 | 113.0 | 40.0 |
| 3.0 | 78.4 | 94.2 | 33.3 |
| 3.5 | 67.2 | 80.7 | 28.6 |
| 4.0 | 58.8 | 70.6 | 25.0 |
| 4.5 | 52.3 | 62.8 | 22.2 |
| 5.0 | 47.0 | 56.5 | 20.0 |
| 5.5 | 42.8 | 51.4 | 18.2 |
| 6.0 | 39.2 | 47.1 | 16.7 |
| 6.5 | 36.2 | 43.5 | 15.4 |
| 7.0 | 33.6 | 40.4 | 14.3 |
| 7.5 | 31.4 | 37.7 | 13.3 |
| 8.0 | 29.4 | 35.3 | 12.5 |
| 9.0 | 26.1 | 31.4 | 11.1 |
| 10.0 | 23.5 | 28.2 | 10.0 |
| 12.0 | 19.6 | 23.5 | 8.3 |
| 15.0 | 15.7 | 18.8 | 6.7 |
| 20.0 | 11.8 | 14.1 | 5.0 |
Quick example: 6.5 L/100 km is approximately 36.2 US MPG, 43.5 UK MPG or 15.4 km/L. The displayed values are suitable for comparison; use the formulas or calculator for additional decimal places.
Measure consumption, price a route or learn the energy boundary
This page is a static unit reference. Use a calculator for your own interval, then keep fuel economy separate from powertrain energy and ownership cost.
US MPG to L/100 km conversion table
Use this table when the source explicitly says US MPG, US gallon or comes from a US fuel-economy context. The UK MPG column shows why the gallon convention must travel with the number.
| US MPG | L/100 km | km/L | Equivalent UK MPG |
|---|---|---|---|
| 10 | 23.52 | 4.25 | 12.0 |
| 15 | 15.68 | 6.38 | 18.0 |
| 20 | 11.76 | 8.50 | 24.0 |
| 25 | 9.41 | 10.63 | 30.0 |
| 30 | 7.84 | 12.75 | 36.0 |
| 35 | 6.72 | 14.88 | 42.0 |
| 40 | 5.88 | 17.01 | 48.0 |
| 45 | 5.23 | 19.13 | 54.0 |
| 50 | 4.70 | 21.26 | 60.0 |
| 55 | 4.28 | 23.38 | 66.1 |
| 60 | 3.92 | 25.51 | 72.1 |
| 70 | 3.36 | 29.76 | 84.1 |
| 80 | 2.94 | 34.01 | 96.1 |
For example, 30 US MPG converts to about 7.84 L/100 km. It does not convert to 30 UK MPG: the equivalent figure is approximately 36.0 UK MPG because an Imperial gallon contains more fuel.
UK MPG to L/100 km conversion table
This lookup is for Imperial MPG, commonly labelled UK MPG, mpg (Imp) or miles per Imperial gallon. If an advert or owner report says only “MPG”, confirm the market and gallon before comparing it with another car.
| UK MPG | L/100 km | km/L | Equivalent US MPG |
|---|---|---|---|
| 20 | 14.12 | 7.08 | 16.7 |
| 25 | 11.30 | 8.85 | 20.8 |
| 30 | 9.42 | 10.62 | 25.0 |
| 35 | 8.07 | 12.39 | 29.1 |
| 40 | 7.06 | 14.16 | 33.3 |
| 45 | 6.28 | 15.93 | 37.5 |
| 50 | 5.65 | 17.70 | 41.6 |
| 55 | 5.14 | 19.47 | 45.8 |
| 60 | 4.71 | 21.24 | 50.0 |
| 70 | 4.04 | 24.78 | 58.3 |
| 80 | 3.53 | 28.32 | 66.6 |
A useful checkpoint is 60 UK MPG: it is about 4.71 L/100 km and 50.0 US MPG. That roughly 20% numerical gap between the two MPG conventions is caused by gallon size, not different vehicle performance.
Exact fuel economy conversion formulas
The conversion is reciprocal. Doubling an MPG figure halves L/100 km; adding a fixed number of MPG does not reduce L/100 km by a fixed amount. This is why a lookup table has uneven gaps.
The same constant works in both directions because the quantities are inversely related. Keep full precision during the calculation and round only the final answer.
Why US MPG and UK MPG are different
Both units count miles travelled per gallon, but they do not use the same gallon. A US liquid gallon is exactly 3.785411784 litres. An Imperial gallon is exactly 4.54609 litres, about 20.1% larger. A vehicle travelling the same distance on the same litres therefore receives a numerically higher Imperial MPG value.
That difference is a unit issue, not an efficiency gain. If one listing quotes 40 US MPG and another quotes 40 UK MPG, the first represents about 5.88 L/100 km while the second represents about 7.06 L/100 km. The US figure describes the more economical result in that particular comparison.
Country alone is a useful clue but not proof. Imported vehicles, international review sites and user-configurable dashboards may show a convention different from the reader’s location. Look for “US”, “Imp”, “UK”, gallon volume or a simultaneous L/100 km figure.
How to compare fuel economy figures correctly
- Identify the unit and gallon. Do not treat an unspecified MPG number as complete.
- Convert both figures to one convention. L/100 km is often the clearest common denominator for fuel volume and distance.
- Match the test basis. Compare combined with combined, city with city and motorway or highway with the equivalent cycle.
- Keep rated and actual figures separate. A laboratory or label result and a fill-to-fill result answer different questions.
- Round at the end. Early rounding can distort cost estimates over a long annual distance.
Official combined values are not necessarily the simple arithmetic average of city and highway figures. A published test procedure can apply its own weighting and corrections. Converting the final official number changes only its unit; it does not make it directly comparable with a result produced under another test cycle.
Fuel type does not alter the conversion formula. Petrol, diesel and the combustion portion of a conventional hybrid can all be expressed in these units. A plug-in hybrid also consumes electricity, so fuel-only MPG or L/100 km does not describe its total energy use unless the driving and charging assumptions are stated.
Worked conversion examples
Example 1: 8.2 L/100 km to MPG
US MPG = 235.214583 ÷ 8.2 = 28.6847. Rounded to one decimal, the result is 28.7 US MPG. UK MPG = 282.480936 ÷ 8.2 = 34.4489, or 34.4 UK MPG.
Example 2: 42 US MPG to metric consumption
L/100 km = 235.214583 ÷ 42 = 5.6003. The converted result is 5.60 L/100 km, and km/L = 100 ÷ 5.6003 = 17.86 km/L.
Example 3: 50 UK MPG to US MPG
First convert to 5.6496 L/100 km, then divide 235.214583 by that result. The equivalent is 41.63 US MPG. Writing “50 MPG” without the gallon would hide this difference.
Small discrepancies between a worked answer and the table come from the table’s display rounding, not from a different formula.
When the table is enough—and when it is not
The table is useful for reading an overseas specification, checking a dashboard setting, interpreting a road test or making a quick like-for-like comparison. It deliberately contains no input form and does not calculate how much fuel your vehicle actually used.
For a real-world measurement, record the distance driven and the volume needed to refill the tank to a comparable level. The Fuel Consumption Calculator performs that calculation and can then express the result in all four units. Use the Trip Cost Calculator when price, route length, return travel or passengers matter.
Neither a conversion nor one tank establishes a vehicle’s permanent economy. Traffic, speed, temperature, tyres, load, terrain, short journeys, auxiliary equipment and refuelling variation can all change measured consumption.
Common conversion mistakes
| Mistake | Why it fails | Better check |
|---|---|---|
| Using 235.2 for UK MPG | That constant belongs to the US gallon. | Use 282.480936 for Imperial MPG. |
| Multiplying MPG by a fixed factor | MPG and L/100 km are reciprocal measures. | Divide the correct constant by the source value. |
| Reading a lower MPG as better | MPG measures distance per fuel volume. | Higher MPG is better; lower L/100 km is better. |
| Comparing city MPG with combined MPG | The driving bases differ. | Match the test category before converting. |
| Rounding the source before conversion | The error carries into the converted value. | Use the original precision and round once. |
Limits of this reference table
- Only selected values are shown; figures between rows require interpolation or the exact formula.
- Displayed results are rounded and are not intended for regulatory certification.
- The table converts units but does not reconcile different vehicle test procedures.
- It does not estimate fuel cost, carbon emissions, range or total vehicle energy use.
- It does not include electric-only units such as kWh/100 km or miles/kWh.
- Real consumption can differ materially from a brochure, label or dashboard value.
Treat the page as a transparent unit reference. For purchase or operating-cost decisions, compare like-for-like source data and calculate with your own distance, energy price and driving pattern.