If you have ever shopped for a European car, read an owner's manual from abroad, or compared a US window sticker with a Canadian or British spec sheet, you have hit the wall: American cars are rated in miles per gallon (MPG), while almost every other country on Earth rates fuel economy in liters per 100 kilometers (L/100km). These two units do not simply use different labels — they measure the same idea in opposite directions. MPG tells you how far a car goes on one gallon of fuel (a higher number is better). L/100km tells you how much fuel a car burns over a fixed 100 km (a lower number is better). Converting between them is not a subtraction or a scaling; it is a reciprocal, which is why a quick mental "divide by 4" guess is almost always wrong.
This calculator performs the conversion exactly, using the internationally agreed constants: 1 US liquid gallon = 3.785411784 liters, and 1 statute mile = 1.609344 kilometers. Plug in the US MPG figure, and the result card instantly shows the equivalent L/100km, the reciprocal kilometers-per-liter, and — once you add your annual mileage and local pump price — the gallons, liters, and dollars you burn in a typical year.
How to Use
- Enter the Miles per Gallon (US) figure. Use the EPA combined rating from the window sticker, not the city-only or highway-only number, unless you specifically want to compare those cycles.
- Optionally set Miles Driven per Year. The US average is about 13,500 miles per year; we default to a round 12,000 miles, but commuters can raise it to 15,000–20,000 and retirees who drive mainly locally can drop it to 5,000–8,000.
- Optionally set Fuel Price in dollars per US gallon. Check the lowest or highest station near your commute and run the tool twice to bracket your real annual fuel cost.
- Read the result card: the highlighted Liters per 100 km is the metric fuel-economy number you would see on a European or Canadian spec sheet. Below it you get kilometers per liter, plus the annual gallons, annual liters, and annual fuel cost derived from your mileage and pump price.
The conversion is a pure division: L/100km = 235.214583 ÷ MPG. That magic number 235.21 comes from folding the two conversion constants together: 100 × 3.785411784 ÷ 1.609344. Because the relationship is reciprocal, a small change in MPG at the low end moves L/100km dramatically, while the same change at the high end barely moves it at all.
Why the Reciprocal Matters
Most Americans intuitively think "50 MPG is twice as efficient as 25 MPG." In L/100km terms that is wrong. 25 MPG is 9.41 L/100km, and 50 MPG is 4.70 L/100km — so going from 25 to 50 MPG halves fuel use. But going from 10 MPG to 20 MPG (also doubling the MPG number) drops consumption from 23.52 L/100km to 11.76 L/100km — halving it again, but saving far more liters per 100 km. This is why regulators in Europe use L/100km: the number moves linearly with fuel actually burned, so comparing a 10 L/100km truck with a 5 L/100km sedan tells you immediately the sedan uses half the fuel for the same distance.
A practical rule of thumb: improving from 20 MPG to 25 MPG on a car driven 12,000 miles a year saves about 240 gallons of fuel annually. Improving from 40 MPG to 50 MPG on the same mileage saves only 60 gallons. Big gains hide in the inefficient cars, not the already-efficient ones.
Examples
Example 1 — A typical sedan at 25 MPG. A family sedan rated at 25 MPG US converts to 9.41 L/100km. Driven 12,000 miles per year at $3.50 per gallon, it burns 480 gallons — about 1,817 liters — and costs roughly $1,680 per year at the pump. That 9.4 L/100km figure would read as "moderate consumption" on a European spec sheet, in line with a compact family car.
Example 2 — A hybrid at 40 MPG. A hybrid rated at 40 MPG US converts to 5.88 L/100km — about 37% less fuel per kilometer than the sedan. On the same 12,000 miles at $3.50/gal, it uses 300 gallons (about 1,136 liters) and costs about $1,050 per year, saving the owner around $630 annually versus the 25 MPG car. Over a ten-year ownership span that is more than $6,000 in saved fuel, before any maintenance differences.
Example 3 — A large pickup at 10 MPG. A heavy pickup rated at 10 MPG US converts to 23.52 L/100km — the kind of number that surprises American drivers but is routine for metric readers. On 12,000 miles at $3.50/gal it swallows 1,200 gallons (about 4,542 liters) and costs about $4,200 per year in fuel. Stepping that same truck up to 15 MPG cuts annual fuel cost to roughly $2,800 — a $1,400 saving — which is exactly why the reciprocal relationship punishes low-MPG vehicles so hard.
FAQ
How do you convert US MPG to L/100km?
Divide 235.214583 by the US MPG value. For example, 25 MPG becomes 235.214583 ÷ 25 = 9.41 L/100km, 40 MPG becomes 5.88 L/100km, and 10 MPG becomes 23.52 L/100km. The factor 235.21 comes from 100 × 3.785411784 liters per US gallon ÷ 1.609344 kilometers per mile.
Is US MPG the same as UK (imperial) MPG?
No. A US gallon is 3.785 liters, while an imperial (UK/Canadian pre-2010) gallon is 4.546 liters. The imperial MPG number is therefore about 20% higher for the exact same car. This calculator uses US gallons, the figure on every American EPA window sticker. If your source is a UK spec sheet, multiply the quoted imperial MPG by 0.8327 to get US MPG before converting.
Why is L/100km a better comparison than MPG?
Because L/100km is a direct measure of fuel used per distance, so the number scales linearly. Going from 20 L/100km to 10 L/100km exactly halves your fuel bill for the same driving. In MPG terms the same halving looks like 10 MPG jumping to 20 MPG — but jumping from 30 to 45 MPG saves far less fuel than jumping from 15 to 20 MPG, even though both feel like similar improvements.
What is a good L/100km figure for a modern car?
A typical US sedan around 25–30 MPG lands near 8–9 L/100km. A modern hybrid at 45–55 MPG lands near 4–5 L/100km. A compact diesel in Europe commonly sits around 4–6 L/100km, while a large pickup or performance truck often exceeds 15 L/100km. Battery-electric cars are not rated in L/100km at all; they use kWh/100km instead.
How much money will I save per year by switching to a more efficient car?
Enter your current MPG, your annual miles, and your local fuel price, then run the same numbers for the new car's MPG. On 12,000 miles at $3.50/gal, each 1 MPG improvement around 25 MPG saves roughly $23 per year, while each 1 MPG improvement around 15 MPG saves roughly $63 per year. The savings compound because you are replacing the car's whole fuel budget, not just trimming it.
Does this calculator work for electric vehicles?
Not directly. EV energy use is measured in kilowatt-hours per 100 km (kWh/100km), not liters of gasoline. You can still use the output as a rough apples-to-apples benchmark — 5 L/100km gasoline is commonly compared to about 15–18 kWh/100km electric — but pair it with a dedicated EV cost-per-mile tool for an accurate dollar comparison.
Disclaimer
This MPG to L/100km calculator is provided for informational purposes only and does not constitute financial, automotive, or tax advice. Conversion results use the standard international constants (1 US gallon = 3.785411784 L, 1 mile = 1.609344 km); EPA ratings, real-world fuel economy, and pump prices vary by driving style, weather, terrain, vehicle condition, and location. Annual fuel cost figures are estimates based on the inputs you enter. Always verify fuel economy and running costs with the vehicle manufacturer, your local fuel prices, and a qualified professional before making a purchase decision.