Liters per 100 km to Miles per gallon (UK)
L/100km
mpg
Conversion History
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Quick Reference Table (Liters per 100 km to Miles per gallon (UK))
| Liters per 100 km (L/100km) | Miles per gallon (UK) (mpg) |
|---|---|
| 4 | 70.62023407 |
| 6 | 47.08015604666666666667 |
| 7 | 40.35441946857142857143 |
| 8 | 35.310117035 |
| 10 | 28.248093628 |
| 12 | 23.54007802333333333333 |
| 15 | 18.83206241866666666667 |
About Liters per 100 km (L/100km)
Liters per 100 kilometers (L/100km) is the standard fuel consumption unit across the European Union, Australia, Canada, China, and most of the metric world. It expresses how many liters of fuel a vehicle burns to travel 100 km — a lower number indicates greater efficiency. Modern petrol passenger cars range from about 4 L/100km for efficient small cars to 15 L/100km or more for large SUVs and trucks. Because the unit measures consumption rather than efficiency, its relationship with km/L and mpg is non-linear: a change from 15 to 10 L/100km saves more fuel per kilometer than a change from 6 to 5 L/100km.
A Toyota Prius averages about 4.5 L/100km under EU testing. A full-size petrol SUV typically consumes 10–14 L/100km on the combined WLTP cycle.
About Miles per gallon (UK) (mpg)
Miles per gallon (imperial) — also written UK mpg — is the traditional British fuel economy unit, using the imperial gallon of 4.546 liters rather than the smaller US gallon (3.785 L). Because the imperial gallon is approximately 20% larger, UK mpg figures are roughly 20% higher than US mpg for the same vehicle: a car rated at 40 US mpg is approximately 48 UK mpg. The UK officially adopted L/100km for type-approval testing under EU harmonisation, but UK mpg remains prevalent in British automotive journalism, used-car listings, and consumer conversations in the United Kingdom and Ireland.
A typical family hatchback in the UK achieves 45–55 mpg (imperial) on the WLTP combined cycle. A 60 UK mpg rating equates to approximately 50 US mpg or 4.7 L/100km.
Liters per 100 km – Frequently Asked Questions
Does fuel consumption increase linearly with speed, or is there a sweet spot?
There is a sweet spot, typically between 50 and 80 km/h for most cars. Below that, the engine runs inefficiently at low load. Above it, aerodynamic drag — which scales with the square of speed — dominates. At 120 km/h a car may use 7 L/100km; at 160 km/h the same car could burn 11+ L/100km. That is why the jump from 100 to 130 km/h costs far more fuel than from 70 to 100.
What L/100km should I expect in real-world driving vs the WLTP sticker?
Most drivers see 10–25% higher consumption than the WLTP rating. A car rated at 6 L/100km will likely average 6.6–7.5 L/100km in mixed real-world conditions. Cold weather, city driving, roof boxes, and aggressive acceleration all push the number up.
How do I convert L/100km to US mpg in my head?
Divide 235 by the L/100km value. So 8 L/100km is roughly 235 ÷ 8 ≈ 29 mpg. For UK mpg, divide 282 instead. This mental shortcut is accurate enough for casual comparisons when shopping for cars across markets.
Why did Europe pick 100 km as the reference distance?
One hundred kilometers is a psychologically round number that keeps consumption figures in a convenient 3–20 range for most passenger cars. Using L/km would give tiny decimals (0.07), and L/1000km would give unwieldy large ones (70). The 100 km base hits the sweet spot for human readability.
What L/100km does a diesel car achieve compared to petrol?
Diesel engines are typically 15–25% more fuel-efficient than equivalent petrol engines. A petrol car rated at 7 L/100km might have a diesel counterpart at 5.5–6 L/100km. However, diesel fuel contains about 13% more energy per liter, so the CO₂ gap is smaller than the L/100km numbers suggest.
Miles per gallon (UK) – Frequently Asked Questions
Why is UK mpg different from US mpg for the same car?
The imperial gallon (4.546 L) is 20.1% larger than the US gallon (3.785 L). So a car that travels 40 miles on a US gallon would travel 40 miles on less than one imperial gallon, yielding a higher UK mpg number. Same car, same fuel, different gallon definitions — endlessly confusing.
Is UK mpg still used now that Britain uses liters at the pump?
Yes, stubbornly so. British fuel is sold in liters and road signs show miles, but most Brits still discuss fuel economy in mpg (imperial). It is a quirky holdover — they buy liters, drive miles, and mentally calculate in a unit that directly matches neither.
How do I convert UK mpg to L/100km?
Divide 282.5 by the UK mpg value. So 50 UK mpg equals 282.5 ÷ 50 = 5.65 L/100km. For US mpg, divide 235.2 instead. These magic numbers are worth memorising if you cross-shop cars between markets.
Why did UK diesel car sales collapse after 2017 despite their higher mpg?
The Volkswagen emissions scandal (2015) shattered public trust in diesel. The UK government then announced clean-air zones charging diesel cars extra, raised vehicle excise duty on new diesels, and signalled a 2030 petrol/diesel ban. Residual values cratered, making diesel a bad financial bet despite 15–20% better mpg. Diesel's UK market share fell from 48% in 2015 to under 10% by 2023, replaced by hybrids and EVs.
Why do British car magazines show different mpg than the manufacturer claims?
Manufacturers quote official WLTP lab test results, while magazines run real-world tests with varying conditions. Magazine figures are usually 10–20% worse than WLTP because they include cold starts, traffic, motorway speeds above test assumptions, and actual British weather.