I'm buying a classic British car rated 45 mpg (Imperial) and want to compare it to a Japanese car rated 16 km/L. Which is more efficient?

45 × 0.354006 = 15.9 km/L. The Japanese car at 16 km/L is very slightly more efficient. Both are excellent — effectively equivalent for practical purposes.

Why is the conversion factor 0.354 and not a round number?

It comes from combining two unit relationships: 1 mile = 1.60934 km and 1 Imperial gallon = 4.546 L. So 1 mpg (Imperial) = 1.60934 km ÷ 4.546 L = 0.354006 km/L. There's no simpler form because both conversions involve irrational ratios.

My British motorhome manual quotes 25 mpg (Imperial). How much fuel will I use driving 500 km in France?

25 mpg (Imperial) × 0.354006 = 8.85 km/L. To drive 500 km: 500 ÷ 8.85 = 56.5 litres. At French fuel prices, you can multiply that by the per-litre cost to estimate your total fuel bill. Alternatively, convert to L/100km: 100 ÷ 8.85 = 11.3 L/100km, and calculate 5 × 11.3 = 56.5 litres.

Do any Asian countries use mpg (Imperial)?

Not as an official standard. India, Japan, South Korea, and Southeast Asia all use km/L. Historically, some British colonial territories used Imperial measures, but metrication replaced mpg (Imperial) in those markets decades ago. Today it's essentially unique to the UK among major automotive markets. See also: [mpg (Imperial) to L/100km](/fuel/mpg-imperial-to-l-per-100km/).

MPG (Imperial) to km/L Converter

Enter a value to instantly convert between fuel economy units.

From

Precision4 dp

1 MPG (Imperial) = 0.354 Km per Liter

Key Formulas

MPG (US) → Liters per 100km

L/100km = mpg × 235.215

Liters per 100km → MPG (US)

mpg = L/100km × 235.215

Km per Liter → MPG (US)

mpg = km/L × 2.35215

MPG (US) → Km per Liter

km/L = mpg × 0.425144

Formula

km/L = mpg (Imperial) × 0.354006

UK car reviews, DVLA fuel economy figures, and older Commonwealth vehicle specs all publish efficiency in miles per Imperial gallon. If you're comparing one of these vehicles to a car from Japan, South Korea, or India — where fuel economy is quoted in kilometres per litre — you need to convert between the two. The Imperial gallon holds 4.546 litres and one mile is 1.60934 km, giving a conversion factor of 0.354006. Because both km/L and mpg (Imperial) are 'distance per volume' metrics (higher is better), there's no inversion — just multiplication.

Source: NIST SP 811, Table B.8

Last reviewed: 2026-06-11 · see our methodology

Frequently Asked Questions

Real-World Examples

A UK family car rated 40 mpg (Imperial) converts to 14.2 km/L — solid mid-range efficiency by Japanese market standards.

40 mpg imp = 14.16 km/L

A UK turbodiesel at 55 mpg (Imperial) achieves 19.5 km/L, competitive with the best petrol-electric hybrids sold in Japan.

55 mpg imp = 19.47 km/L

A UK SUV at 30 mpg (Imperial) converts to 10.6 km/L — average for larger vehicles in the Japanese domestic market.

30 mpg imp = 10.62 km/L

A UK plug-in hybrid at 60 mpg (Imperial) on the official test yields 21.2 km/L, rivalling the Toyota Prius' Japanese JC08 rating.

60 mpg imp = 21.24 km/L

mpg to l per 100km l per 100km to mpg kml to mpg mpg to kml

MPG (Imperial) to km/L Converter

Key Formulas

Formula

Frequently Asked Questions

Real-World Examples

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