Fuel Economy Units
| Unit | Used in | Higher = better? |
|---|---|---|
| MPG (US gallons) | United States | Yes — higher MPG = more efficient |
| MPG (Imperial gallons) | United Kingdom, Canada (older) | Yes — higher = better |
| L/100km | Europe, Canada, Australia | No — lower = more efficient |
| km/L | Japan, some Asian countries | Yes — higher = better |
| miles/litre | Rare; UK transition metric | Yes — higher = better |
Key Conversions
| US MPG | L/100km | km/L | UK MPG |
|---|---|---|---|
| 10 | 23.52 | 4.25 | 12.01 |
| 20 | 11.76 | 8.50 | 24.02 |
| 30 | 7.84 | 12.75 | 36.03 |
| 40 | 5.88 | 17.00 | 48.05 |
| 50 | 4.70 | 21.25 | 60.06 |
| 60 | 3.92 | 25.50 | 72.07 |
Why US MPG and UK MPG Differ
The US gallon (3.785 litres) is smaller than the Imperial gallon used in the UK (4.546 litres). A car that gets 30 US MPG would get about 36 UK MPG — the same fuel efficiency, just expressed in different gallon sizes. Always check which gallon a spec sheet uses when comparing vehicles across countries.
Frequently Asked Questions
What is a good MPG?
For US vehicles in 2026: compact cars achieve 30–40 MPG combined; hybrids reach 45–60 MPG; full EVs are rated in MPGe (miles per gallon equivalent). SUVs average 22–30 MPG. The EPA average for all new passenger vehicles sold in the US is around 28–30 MPG combined.
How do I convert L/100km to MPG?
US MPG = 235.21 / L/100km. So 7 L/100km = 235.21/7 = 33.6 US MPG. This works because 1 US gallon = 3.78541 litres and 1 mile = 1.60934 km, giving the constant 235.21 (= 100 × 3.78541 / 1.60934).
What is MPGe for electric vehicles?
MPGe (miles per gallon equivalent) converts EV energy consumption to a comparable unit. 1 gallon of gasoline contains 33.7 kWh of energy, so an EV using 33.7 kWh to travel 100 miles would be rated 100 MPGe. Most EVs achieve 90–130 MPGe — 3–4× more efficient than gasoline cars.