MPG (US)
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Converted fuel economy
Convert Imperial miles per gallon to US miles per gallon instantly
Accurately convert MPG UK to US and back using the exact Imperial and US gallon ratio. Includes formula, reference table, and full bidirectional calculator for 2026.
Precise fuel economy conversion between Imperial and US gallon standards
Convert MPG UK to US using the exact ratio of 0.832674, derived from the difference between the Imperial gallon (4.54609 litres) and the US gallon (3.78541 litres). Every result is mathematically precise for real-world fuel economy comparisons.
Switch seamlessly between MPG UK to US and US to UK conversion modes. Whether you are comparing a British car's fuel rating to an American one, or planning a cross-border road trip, this tool handles both directions instantly.
Essential for car buyers, importers, fleet managers, and travellers comparing vehicle fuel efficiency across the UK and USA. Also useful for converting manufacturer specs from one market to another in 2026.
Select conversion direction and enter your MPG value below
The key reason MPG UK and MPG US differ is that the UK Imperial gallon and the US gallon are not the same volume. One Imperial gallon equals 4.54609 litres, while one US gallon equals only 3.78541 litres. This means the Imperial gallon is approximately 20.09% larger than the US gallon. Because a UK car travels the same distance using a larger unit of fuel, its MPG figure is always higher than the equivalent US MPG rating for the same vehicle.
To convert MPG UK to US, you multiply by the ratio of US gallon to Imperial gallon: 3.78541 ÷ 4.54609 = 0.832674. This is why a car rated at 40 MPG in the UK only achieves around 33.3 MPG by US standards. For related unit conversions, see the atmospheres to pascals converter for other Imperial vs metric comparisons.
The Imperial gallon is 20.09% larger than the US gallon — so UK MPG is always higher than US MPG for the same vehicle.
Converting between UK and US miles per gallon is a straightforward multiplication. Follow these steps to convert any MPG UK figure to its US equivalent without a calculator.
Use this table for instant MPG UK to US conversions across the most common fuel economy ratings. The desktop table shows full data; on mobile, use the card view below.
| MPG (UK) | MPG (US) | L/100km | km/L | Difference |
|---|---|---|---|---|
| 10 MPG (UK) | 8.33 MPG (US) | 28.25 L/100km | 3.54 km/L | –1.67 MPG |
| 20 MPG (UK) | 16.65 MPG (US) | 14.13 L/100km | 7.08 km/L | –3.35 MPG |
| 25 MPG (UK) | 20.82 MPG (US) | 11.30 L/100km | 8.85 km/L | –4.18 MPG |
| 30 MPG (UK) | 24.98 MPG (US) | 9.42 L/100km | 10.63 km/L | –5.02 MPG |
| 35 MPG (UK) | 29.14 MPG (US) | 8.07 L/100km | 12.39 km/L | –5.86 MPG |
| 40 MPG (UK) | 33.31 MPG (US) | 7.07 L/100km | 14.16 km/L | –6.69 MPG |
| 45 MPG (UK) | 37.47 MPG (US) | 6.28 L/100km | 15.93 km/L | –7.53 MPG |
| 50 MPG (UK) | 41.63 MPG (US) | 5.65 L/100km | 17.70 km/L | –8.37 MPG |
| 55 MPG (UK) | 45.80 MPG (US) | 5.14 L/100km | 19.47 km/L | –9.20 MPG |
| 60 MPG (UK) | 49.96 MPG (US) | 4.71 L/100km | 21.24 km/L | –10.04 MPG |
| 70 MPG (UK) | 58.29 MPG (US) | 4.04 L/100km | 24.78 km/L | –11.71 MPG |
| 80 MPG (UK) | 66.61 MPG (US) | 3.53 L/100km | 28.32 km/L | –13.39 MPG |
One UK Imperial gallon equals 4.54609 litres. This is the standard unit used for MPG (UK) fuel economy ratings on all British vehicles and manufacturer specifications sold in the United Kingdom.
One US gallon equals 3.78541 litres. All American vehicle fuel economy ratings (MPG US) are based on this smaller gallon, which is why the same car will always show a lower MPG figure in the USA than in the UK.
The Imperial gallon is approximately 20.09% larger than the US gallon. As a result, any MPG (UK) figure is always about 20% higher than the equivalent MPG (US) figure for the same vehicle and the same driving conditions.
The exact conversion factor is 0.832674 (UK → US) and 1.20095 (US → UK). These are derived directly from the ratio of the two gallon sizes and are the internationally recognised values used in fuel economy conversions.
A popular UK family car rated at 50 MPG (UK) would only achieve 41.63 MPG (US) by American standards. This distinction is critical when comparing vehicles across markets or reading manufacturer specs from different regions.
To also convert to litres per 100 km (used across Europe and Australia), use: L/100km = 282.481 ÷ MPG (UK) or L/100km = 235.215 ÷ MPG (US). For example, 40 MPG (UK) = 7.06 L/100km.
With international car buying, importing, and cross-border travel more common than ever in 2026, understanding the difference between UK and US MPG ratings is essential. Many online car reviews, manufacturer websites, and fuel economy databases publish figures in only one standard, making direct comparison impossible without conversion.
Never compare UK MPG directly with US MPG without converting first. A car advertised as "50 MPG" in the UK and "40 MPG" in the US may actually be the same vehicle — the difference is purely the gallon size used in each country, not the vehicle's actual fuel efficiency.
The UK and USA share many unit names — like gallons and miles — but the values differ. Always verify which standard a fuel economy figure uses before making comparisons or calculations.
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