Last updated: May 2026
Convert between MPG, L/100km, km/L, and miles per liter. Covers US MPG, Imperial MPG, and metric fuel economy.
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All conversions are anchored to US MPG. Every unit derives from a fixed mathematical relationship with US MPG:
L/100km = 235.214 ÷ US MPG — this constant comes from converting gallons to liters (3.78541) and miles to kilometers (1.60934), then scaling to 100 km: (100 × 3.78541) ÷ 1.60934 = 235.214.
km/L = US MPG × 0.425144 — one mile per US gallon equals 0.425144 kilometers per liter.
Imperial MPG = US MPG × 1.20095 — a UK gallon (4.54609 L) is larger than a US gallon (3.78541 L), so Imperial MPG is always higher: 4.54609 ÷ 3.78541 ≈ 1.20095.
Miles per liter = US MPG ÷ 3.78541 — divide out the gallons-to-liters factor.
Fuel efficiency is one of the most fragmented measurement areas on the planet. Drive a rental car from the US to Canada and suddenly "how far can I go on a tank" requires a unit conversion. Buy a European car spec sheet and the L/100km number looks completely alien if you're used to MPG. It's not arbitrary — each system reflects a different philosophy about what "efficiency" means.
The United States uses US MPG, where a gallon is 3.785 liters. The UK uses Imperial MPG, where a gallon is larger at 4.546 liters — which means a British gallon gets you about 20% further, making UK cars sound more efficient than they are when compared to American ratings directly. Most of Europe, Asia, and Australia use L/100km, which inverts the logic entirely: instead of "how far per unit of fuel," you're measuring "how much fuel per unit of distance."
That inversion matters more than it seems. With MPG, doubling your fuel economy from 15 to 30 MPG saves as much gas per mile as going from 30 to infinity. The L/100km scale is linear in fuel consumption — cutting from 10 L/100km to 5 L/100km saves exactly as much fuel as cutting from 5 to 2.5 L/100km over the same distance. Neither system is wrong; they just answer different questions.
How does your car stack up? Here's a reference chart across all five units for common vehicle categories:
| Vehicle Type | US MPG | Imp. MPG | L/100km | km/L |
|---|---|---|---|---|
| City car (e.g. Mitsubishi Mirage) | 39 | 46.8 | 6.03 | 16.58 |
| Compact sedan (e.g. Honda Civic) | 33 | 39.6 | 7.13 | 14.03 |
| Mid-size sedan (e.g. Toyota Camry) | 30 | 36.0 | 7.84 | 12.75 |
| Crossover SUV (e.g. Toyota RAV4) | 27 | 32.4 | 8.71 | 11.48 |
| Full-size truck (e.g. Ford F-150 V8) | 18 | 21.6 | 13.07 | 7.65 |
| Hybrid (e.g. Toyota Prius) | 52 | 62.4 | 4.52 | 22.11 |
| EV equivalent (e.g. Tesla Model 3) | 134 MPGe | 160.9 | 1.76 | 56.97 |
Note: EV figures use MPGe (miles per gallon equivalent) based on 33.7 kWh per gallon of energy. L/100km equivalent is for energy consumption comparison only.
The US EPA sets Corporate Average Fuel Economy (CAFE) standards — the fleet-wide average all automakers must meet. As of 2026, the combined target for passenger cars is approximately 49 MPG, with SUVs and light trucks at roughly 39 MPG. In practice, most mainstream vehicles fall below these targets, with automakers using credits from electric vehicle sales to stay in compliance.
The EU uses a CO₂ emissions standard (grams per km) rather than a direct fuel economy requirement, but the practical equivalent for 2025 onwards is roughly 4.1 L/100km (about 57 US MPG) for new passenger cars. That's a significantly tougher target than the US, which is a big reason why European cars tend to be more fuel-efficient and diesel engines have historically been more common in Europe.
Japan uses the JC08 or WLTC test cycle, which produces figures in km/L. A "good" Japanese fuel economy rating for a non-hybrid is around 18–22 km/L, equivalent to roughly 42–52 US MPG.
What is considered good fuel economy?
For a passenger car in the US, anything above 30 MPG combined is considered good. Compact cars typically hit 30–35 MPG, hybrids reach 40–60 MPG, and plug-in hybrids or EVs can exceed 100 MPGe. In Europe, a strong rating is under 6 L/100km (equivalent to about 39 US MPG). For SUVs and trucks, expectations are lower — 25+ MPG is solid for a midsize crossover, while full-size trucks typically manage 18–22 MPG.
What is the difference between US MPG and Imperial MPG?
A US gallon is 3.785 liters while a UK (Imperial) gallon is 4.546 liters — about 20% larger. This means Imperial MPG is always about 20% higher than US MPG for the same vehicle. A car rated 40 US MPG is equivalent to roughly 48 Imperial MPG. When comparing fuel economy between British and American car reviews, always check which gallon is being used — the difference is significant enough to cause real confusion.
How can I improve my MPG?
Several habits have measurable impact: maintain steady speeds and avoid aggressive acceleration (smooth driving can improve economy by 5–30%); keep tires properly inflated (underinflation costs 0.5–3%); remove unnecessary cargo weight; use cruise control on highways; avoid extended idling; and service the air filter and spark plugs on schedule. On the highway, slowing from 75 mph to 65 mph can improve fuel economy by 10–15% due to reduced aerodynamic drag.
What is MPGe for electric vehicles?
MPGe (miles per gallon equivalent) is the EPA's way of expressing EV efficiency in terms familiar to gas-car owners. The EPA defines one gallon of gasoline as containing 33.7 kWh of energy, so MPGe measures how far an EV travels on 33.7 kWh. A Tesla Model 3 Standard Range gets around 134 MPGe — meaning it goes as far on 33.7 kWh of electricity as a gas car does on one gallon. In practice this means EVs are dramatically more efficient, since electric motors convert ~85–90% of energy to motion versus ~20–40% for combustion engines.
Why does L/100km seem "backwards" compared to MPG?
MPG tells you how far you go per unit of fuel — higher is better. L/100km tells you how much fuel you consume per unit of distance — lower is better. They're mathematical inverses. Europeans prefer L/100km because it makes fuel cost calculations straightforward: multiply L/100km by distance (in hundreds of km) by price per liter to get total cost. There's also a perception argument: L/100km makes small improvements in efficient cars more visible on the scale, while MPG makes the same improvements look larger for inefficient vehicles (the so-called "MPG illusion").