Litres per 100km
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Equivalent fuel economy
Accurate fuel economy conversion for imperial miles per gallon to L/100km
Convert MPG (UK) to litres per 100km instantly with precise calculations. Includes bidirectional conversion and detailed fuel economy breakdowns for 2026.
Professional fuel economy conversion for drivers, engineers, and vehicle buyers
Convert miles per imperial gallon to litres per 100km with precision. Our tool uses the exact conversion ratio of 282.481, derived from the imperial gallon (4.54609 litres) and the mile (1.609344 km), delivering accurate results every time.
Switch seamlessly between MPG (UK) to L/100km and L/100km to MPG (UK) conversion modes. Get instant results alongside additional values including MPG (US) and km per litre — all from a single input value.
Essential for UK drivers comparing vehicles, car buyers reviewing EU specs, fleet managers calculating fuel costs, and anyone converting between imperial and metric fuel economy standards in 2026.
Select conversion direction and enter your value below
Miles per gallon (UK) and litres per 100 kilometres are both measurements of fuel economy, but they work in opposite directions. A higher MPG number means better fuel efficiency, while a lower L/100km number means better efficiency. This inverse relationship is why a simple multiplication or division is not enough — the conversion requires a specific formula.
The UK imperial gallon differs from the US gallon: one imperial gallon equals 4.54609 litres, compared to the US gallon at 3.78541 litres. Because of this difference, unit conversions in engineering and science always specify which gallon standard is being used. The exact conversion constant for UK MPG to L/100km is 282.481, derived from the imperial gallon size and the kilometre-to-mile ratio.
Where 282.481 = 100 × 4.54609 litres (imperial gallon) ÷ 1.609344 (km per mile)
To understand where 282.481 comes from: one mile equals 1.609344 kilometres, and one imperial gallon equals 4.54609 litres. When you drive 1 mile per gallon (UK), you are travelling 1.609344 km using 4.54609 litres. To express this as litres per 100km, the calculation is: (4.54609 ÷ 1.609344) × 100 = 282.481. This constant makes the conversion simple — just divide it by your MPG value.
A car achieving 40 MPG (UK):
L/100km = 282.481 ÷ 40 = 7.06 L/100km
A car achieving 60 MPG (UK):
L/100km = 282.481 ÷ 60 = 4.71 L/100km
↑ Higher MPG = Lower L/100km = Better fuel economy
Use this reference table to quickly look up common MPG (UK) values and their equivalent L/100km figures. This is especially useful when comparing vehicle specifications between UK and European car listings.
| MPG (UK) | L/100km | MPG (US) | km per Litre | Efficiency Rating |
|---|---|---|---|---|
| 10 MPG | 28.25 L/100km | 8.33 MPG | 3.54 km/L | Very Poor |
| 15 MPG | 18.83 L/100km | 12.49 MPG | 5.31 km/L | Poor |
| 20 MPG | 14.12 L/100km | 16.65 MPG | 7.08 km/L | Below Average |
| 25 MPG | 11.30 L/100km | 20.82 MPG | 8.85 km/L | Average |
| 30 MPG | 9.42 L/100km | 24.98 MPG | 10.62 km/L | Average |
| 35 MPG | 8.07 L/100km | 29.14 MPG | 12.39 km/L | Good |
| 40 MPG | 7.06 L/100km | 33.31 MPG | 14.16 km/L | Good |
| 45 MPG | 6.28 L/100km | 37.47 MPG | 15.93 km/L | Very Good |
| 50 MPG | 5.65 L/100km | 41.63 MPG | 17.70 km/L | Very Good |
| 55 MPG | 5.14 L/100km | 45.79 MPG | 19.47 km/L | Excellent |
| 60 MPG | 4.71 L/100km | 49.96 MPG | 21.24 km/L | Excellent |
| 65 MPG | 4.35 L/100km | 54.12 MPG | 23.01 km/L | Excellent |
| 70 MPG | 4.04 L/100km | 58.28 MPG | 24.78 km/L | Exceptional |
| 80 MPG | 3.53 L/100km | 66.60 MPG | 28.32 km/L | Exceptional |
| 100 MPG | 2.82 L/100km | 83.26 MPG | 35.40 km/L | Exceptional |
A common source of confusion is the difference between UK MPG and US MPG. Because the imperial gallon (UK) is larger than the US gallon, UK MPG figures are always higher than US MPG for the same car. A vehicle rated at 40 MPG in the UK would only achieve about 33.3 MPG on the US scale. When comparing measurements across different unit systems, it is critical to always confirm which standard is being used.
UK MPG → US MPG: Multiply by 0.8327 (e.g., 40 MPG UK = 33.3 MPG US)
US MPG → UK MPG: Multiply by 1.2009 (e.g., 33.3 MPG US = 40 MPG UK)
Both → L/100km: UK uses constant 282.481 | US uses constant 235.215
One imperial gallon equals exactly 4.54609 litres. This was standardised in the UK Weights and Measures Act 1985. It is approximately 20% larger than the US liquid gallon (3.78541 litres), which is why UK MPG figures always appear higher than US MPG for the same vehicle.
The average new petrol car sold in the UK in 2026 achieves approximately 40–50 MPG (UK), equivalent to roughly 5.6–7.1 L/100km. Hybrid vehicles typically achieve 60–80 MPG (UK), or 3.5–4.7 L/100km, representing a significant improvement over conventional engines.
Most European countries use litres per 100km (L/100km) as the standard fuel economy measure, as it aligns with the metric system. EU regulations and new car labels display fuel consumption in L/100km, making this conversion essential for UK buyers comparing European vehicle specifications.
MPG and L/100km have an inverse relationship — as one increases, the other decreases. This means you cannot compare two cars' fuel efficiency simply by subtracting L/100km values. A drop from 8 to 6 L/100km saves more fuel than a drop from 6 to 4 L/100km over the same distance.
Official UK MPG figures are tested under the WLTP (Worldwide Harmonised Light Vehicle Test Procedure) cycle since 2018. Real-world fuel economy is typically 10–20% lower than official WLTP figures, depending on driving style, speed, load, and road conditions. Always account for this when calculating actual fuel costs.
Learn the difference between UK MPG, US MPG, and L/100km, and understand how fuel economy affects running costs and environmental impact for your vehicle in 2026.
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