How do I convert MPG to L/100km?
L/100km = 235.215 / US MPG, or 282.481 / UK MPG. The two are inverses, so higher MPG corresponds to lower L/100km.
Fuel Economy calculator
Fuel Economy converter
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Fuel economy measures how far a vehicle can travel on a given amount of fuel. The two dominant metrics are miles per gallon (MPG, used in the US and UK) and liters per 100 kilometers (L/100km, used in most of the rest of the world). The two are inverse: MPG goes up as fuel use goes down. To convert US MPG to L/100km, divide 235.215 by the MPG number.
Example fuel economy conversions
1 US MPG0.425 km/L, 235.215 / (L/100km)
1 UK (imperial) MPG0.354 km/L, 282.481 / (L/100km)
20 US MPG11.76 L/100km, 8.5 km/L
30 US MPG7.84 L/100km, 12.75 km/L
Open the live fuel economy converter for any input value.
Why two metrics for the same thing
MPG and L/100km capture the same information but in opposite directions. MPG measures distance per fixed amount of fuel; L/100km measures fuel per fixed distance. Doubling MPG halves L/100km. Both can quote the same car's efficiency, just from different starting points.
L/100km is preferred in most metric countries because it scales linearly with cost: a 1-point improvement at 5 L/100km saves more fuel than a 1-MPG improvement at 50 MPG. MPG is convenient for distance-planning (how far can I go on a tank?) but obscures the marginal value of efficiency gains, especially at high MPG values.
US MPG vs UK MPG
MPG is not a single unit. US MPG uses the US gallon (3.78541 L); UK (imperial) MPG uses the larger imperial gallon (4.54609 L). A car rated 30 UK MPG is roughly 25 US MPG. UK MPG figures look better than US MPG figures for the same car, which causes confusion in cross-market reviews.
Always check the source country before comparing. EPA fuel-economy ratings use US MPG. UK manufacturer specs and most British automotive media use UK MPG. European specs typically use L/100km, sidestepping the issue.
Electric vehicle efficiency
Battery-electric vehicles use different metrics. The EPA reports MPGe (miles per gallon equivalent) by converting electrical energy to gasoline-equivalent energy (1 gallon of gasoline ≈ 33.7 kWh). EU regulations report kWh/100km (the EV equivalent of L/100km for combustion vehicles).
A 2026 efficient EV like a Tesla Model 3 might rate 130 MPGe and 16 kWh/100km. Comparing combustion fuel economy to EV efficiency requires the MPGe conversion because the underlying energy carriers (liquid fuel vs grid electricity) have different cost and emissions profiles.
Common fuel economy conversions
| From | Equivalent |
|---|---|
| 1 US MPG | 0.425 km/L, 235.215 / (L/100km) |
| 1 UK (imperial) MPG | 0.354 km/L, 282.481 / (L/100km) |
| 20 US MPG | 11.76 L/100km, 8.5 km/L |
| 30 US MPG | 7.84 L/100km, 12.75 km/L |
| 40 US MPG | 5.88 L/100km, 17.0 km/L |
| 50 US MPG | 4.70 L/100km, 21.3 km/L |
| 60 US MPG (hybrid territory) | 3.92 L/100km |
| 100 MPGe (EV equivalent) | ≈ 33.7 kWh per 100 miles |
| 10 L/100km | 23.5 US MPG, 28.2 UK MPG, 10 km/L |
| 5 L/100km (excellent) | 47.0 US MPG, 56.5 UK MPG |
Frequently asked questions
Is US MPG or UK MPG bigger?
UK MPG values are larger because the imperial gallon is larger. A car rated 40 UK MPG is about 33.3 US MPG, the same physical efficiency.
Which metric is more useful for fuel cost?
L/100km. It scales linearly with consumption, so a 1-L/100km change at any starting point represents the same absolute fuel savings. MPG's non-linearity means a 5-MPG improvement at 20 MPG saves more fuel than a 5-MPG improvement at 40 MPG.
How do EVs compare to combustion vehicles for efficiency?
EVs convert about 85-90% of input energy into motion; modern combustion engines hit 25-35% under optimal load. Per-mile energy cost for EVs is typically 1/3 to 1/4 of equivalent combustion vehicles, depending on local electricity vs gasoline prices.
What's considered fuel-efficient?
For a 2026 gasoline passenger car: under 6 L/100km (about 40 US MPG) is good. Under 4 L/100km (60+ US MPG) is excellent and usually requires a hybrid powertrain. EVs report kWh/100km separately and aren't directly comparable on the MPG scale without the MPGe conversion.
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