Fuel Economy Converter
Convert between MPG (US/UK), L/100km and km/L.
L / 100 km
7.841
from 30
MPG (US)
30
MPG (UK)
36.03
km / L
12.754
AI Breakdown & Smart Takeaway
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How the Fuel Economy Converter works
The GKCalculators Fuel Economy Converter instantly converts between the world's major fuel efficiency units—US MPG, UK MPG, litres per 100 kilometres (L/100km), and kilometres per litre (km/L)—so drivers, fleet managers, and travellers can meaningfully compare vehicle efficiency across different regional standards.
Fuel economy is expressed differently around the world, and those differences are not merely cosmetic—they reflect fundamentally different ways of thinking about efficiency. In the United States, higher numbers are always better: a car rated at 40 MPG is more efficient than one rated at 25 MPG. In most of Europe, Asia, and Australia, L/100km is standard, and here lower numbers are better—a car consuming 6 L/100km is more efficient than one consuming 9 L/100km. The GKCalculators converter handles this inversion automatically, so you never have to worry about which direction the scale runs.
The conversion between US MPG and L/100km relies on a fixed relationship between US liquid gallons and litres, and between miles and kilometres. One US gallon equals exactly 3.78541 litres, and one mile equals exactly 1.60934 kilometres. Because the US MPG system and the L/100km system are reciprocal in nature—one measures distance per volume, the other measures volume per distance—the conversion formula is not a simple multiplication but a division: L/100km = 235.214 ÷ US MPG. UK (Imperial) MPG uses a larger gallon of 4.54609 litres, which is why a UK MPG figure always looks numerically higher than the equivalent US MPG; the converter applies the correct constant (282.481) for UK conversions to avoid this common source of confusion.
A frequent mistake travellers make is assuming that a car rated at 50 MPG in the UK spec sheet performs the same as a US car rated at 50 MPG—it does not. The UK figure translates to roughly 41.6 US MPG or about 5.65 L/100km. Similarly, people sometimes confuse km/L (common in Japan, India, and parts of Latin America) with L/100km: km/L is the direct distance-per-volume equivalent of MPG, so converting it simply requires taking the reciprocal and scaling by 100 (L/100km = 100 ÷ km/L). The tool handles all four units simultaneously so you can enter any one value and instantly see all three equivalents.
When using this converter for practical decisions—such as comparing a European rental car's quoted fuel consumption to what you're used to at home, or evaluating imported vehicle specs—make sure you also consider the fuel type. Diesel vehicles typically achieve higher MPG or lower L/100km figures than equivalent petrol models because diesel has greater energy density per litre, not necessarily because the engine is proportionally more efficient. Combined cycle figures from official tests also tend to be optimistic by 10–20% versus real-world driving, so treat converted numbers as a useful benchmark rather than an exact prediction of pump costs.
Formula
US MPG to L/100km: L/100km = 235.214 ÷ MPG(US) | UK MPG to L/100km: L/100km = 282.481 ÷ MPG(UK) | km/L to L/100km: L/100km = 100 ÷ km/L | MPG(US) to MPG(UK): MPG(UK) = MPG(US) × 1.20095
Pro tips
- Always confirm whether an MPG figure is US or UK before converting—UK MPG is ~20% higher for the same vehicle, so mistaking one for the other will meaningfully skew any cost or range calculation.
- When comparing a vehicle's official L/100km or MPG rating to your real-world experience, apply a 10–15% real-world adjustment factor; official test figures are measured under controlled conditions that rarely match everyday driving.
- If you're calculating fuel costs for a road trip abroad, convert the destination country's efficiency unit to L/100km first, then multiply by the total kilometres and the local fuel price per litre—this is the most universally compatible approach.
- Fleet managers comparing multiple vehicles should standardise on L/100km internally, since its linear scale makes percentage differences in consumption directly comparable without the distortion that MPG's reciprocal scale introduces at higher efficiency values.
- When evaluating hybrid or plug-in hybrid vehicles, be aware that official combined figures can be especially optimistic because they assume frequent opportunity charging; treat any converted figure for these drivetrains with extra scepticism in real-world planning.
Key terms
- US MPG (Miles Per Gallon)
- — A fuel economy measure used in the United States expressing how many miles a vehicle travels on one US liquid gallon (3.78541 litres) of fuel; higher values indicate greater efficiency.
- UK MPG (Imperial MPG)
- — The British equivalent of MPG, calculated using the larger Imperial gallon (4.54609 litres), which means UK MPG figures are always approximately 20% higher than the equivalent US MPG for the same vehicle.
- L/100km (Litres per 100 Kilometres)
- — The fuel consumption standard used in Europe, Australia, and Canada, expressing how many litres of fuel are required to travel 100 kilometres; lower values indicate greater efficiency.
- km/L (Kilometres per Litre)
- — A fuel economy metric common in Japan, India, and parts of Latin America that measures how far a vehicle travels on one litre of fuel; it is the metric-system analogue of MPG, where higher values are better.
- Reciprocal Relationship
- — The mathematical inverse relationship between distance-per-volume metrics (MPG, km/L) and volume-per-distance metrics (L/100km), meaning you cannot convert between them with simple multiplication—division is required.
- Combined Cycle Rating
- — An official standardised fuel economy figure that blends city and highway driving conditions into a single number, used as the basis for MPG and L/100km labels on new vehicles worldwide.
