A UK car is rated 35 Imperial MPG. How does that compare to a US EPA rating?

35 Imperial MPG = 11.9 km/L. In US terms, this is roughly 28-30 US MPG equivalent (higher number despite same efficiency). The UK uses larger gallons, inflating MPG numbers.

What's the difference between Imperial MPG and US MPG?

1 Imperial gallon = 4.546 L; 1 US gallon = 3.785 L. The same car achieves lower Imperial MPG because an Imperial gallon is bigger. 30 US MPG ≈ 25 Imperial MPG for identical efficiency.

I found a vintage British car rated 45 Imperial MPG. Is that realistic?

45 Imperial MPG ≈ 16 km/L—possible for a small, lightweight, efficient 1980s car. Modern cars of similar size achieve 15-20 km/L. Check if the rating is combined or highway-only (highway ratings are optimistic).

Why would anyone use Imperial MPG instead of L/100km?

Historical inertia. The UK (and some Commonwealth nations) still use Imperial units. Modern standards increasingly use L/100km or CO₂ emissions (g/km), but legacy vehicles and older specs reference Imperial MPG. For L/100km comparisons, try [MPG (Imperial) to L/100km](/fuel/mpg-imperial-to-l-per-100km/).

MPG (Imperial) to Km per Liter 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 (UK) × 0.354006

Miles per gallon exists in two versions: US MPG and Imperial (UK) MPG. Imperial gallons are larger than US gallons (4.546 L vs 3.785 L), so the same car achieves different Imperial vs US MPG ratings. The UK uses Imperial MPG for vehicle efficiency; converting to kilometers per liter (km/L) is essential when comparing British cars with metric-system vehicles. One Imperial MPG equals approximately 0.354 km/L—notably lower than US MPG conversions due to the larger Imperial gallon.

Source: NIST SP 811, Table B.8

Frequently Asked Questions

Real-World Examples

20 Imperial MPG. A typical UK car rating—converts to about 7 km/L, considered average efficiency.

20 mpg imp = 7.08 km/L

30 Imperial MPG. A good UK car efficiency—about 10.6 km/L, typical of modern sedans.

30 mpg imp = 10.62 km/L

40 Imperial MPG. Excellent UK car efficiency—14.2 km/L, typical of efficient hybrids and small diesels.

40 mpg imp = 14.16 km/L

50 Imperial MPG. Exceptional efficiency—17.7 km/L, achievable only by ultra-efficient hybrids or eco-driving.

50 mpg imp = 17.7 km/L

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

MPG (Imperial) to Km per Liter Converter

Key Formulas

Formula

Frequently Asked Questions

Real-World Examples

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