25
mpg
30.02
mpg
9.41
L/100km
10.63
km/L
0.0941
L/km
1,062.9
km
25
mpg
30.02
mpg
9.41
L/100km
10.63
km/L
0.0941
L/km
1,062.9
km
The Fuel Efficiency Converter helps you instantly convert between all major fuel economy metrics used around the world. Whether you need to convert MPG (US) to L/100km for European car shopping, UK MPG to US MPG for comparing imports, or km/L to L/100km for trip cost calculations, this tool provides all conversions simultaneously.
Fuel efficiency is expressed differently depending on the country and convention. MPG (miles per gallon) is used in the United States and United Kingdom — higher MPG means better efficiency. L/100km (liters per 100 kilometers) is the standard in most of Europe, Canada, and Australia — lower values mean better efficiency. km/L (kilometers per liter) is used in some Asian and South American countries — higher values mean better efficiency.
A critical distinction: US and UK gallons are different sizes. 1 US gallon = 3.785 L, while 1 UK gallon = 4.546 L, making UK MPG figures approximately 20% higher than US MPG for the same vehicle. Always specify which MPG you mean when comparing internationally.
All fuel efficiency values are first converted to L/100km as the base unit, then converted to each output. The key insight is that MPG and L/100km are inversely proportional — better efficiency means higher MPG but lower L/100km.
Conversion formulas:
Derivation of 235.215: 1 US gallon = 3.785411784 L, 1 mile = 1.609344 km, so: $$235.215 = \frac{1000 \times 3.785411784}{1.609344}$$
Derivation of 282.481: 1 UK gallon = 4.54609 L, so: $$282.481 = \frac{1000 \times 4.54609}{1.609344}$$
Reference fuel economy values: an efficient compact car achieves 35–45 US MPG (6.7–5.2 L/100km). An average sedan achieves 25–35 US MPG (9.4–6.7 L/100km). An SUV or truck typically gets 15–25 US MPG (15.7–9.4 L/100km). A hybrid car like the Toyota Prius achieves 50–58 US MPG (4.7–4.1 L/100km). The EU fleet average target is approximately 4.1 L/100km (57 US MPG) for new cars by 2030. Better fuel efficiency directly reduces fuel costs and CO₂ emissions.
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A European car rated at 6 L/100km achieves approximately 39.2 US MPG — useful for American buyers comparing European imports against domestic EPA ratings.
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55 UK MPG equals approximately 45.8 US MPG — about 20% less. The difference is due to the larger UK gallon (4.546 L vs. 3.785 L). This is a common source of confusion when comparing fuel economy across markets.
Because a UK gallon (imperial gallon) = 4.546 liters, which is about 20% larger than a US gallon = 3.785 liters. If a car burns the same amount of fuel per mile, it will travel about 20% more miles per UK gallon than per US gallon. Always verify which MPG system is being used when comparing internationally.
Formula: Annual fuel cost = (Annual miles ÷ MPG) × price per gallon. For example: 12,000 miles/year ÷ 30 MPG = 400 gallons × $3.50/gal = $1,400/year. In metric: (Annual km ÷ 100) × L/100km × price per liter. Improving fuel economy from 25 to 35 MPG saves about 137 gallons (520 liters) per 12,000 miles annually.
In the US, the EPA classifies fuel economy as: excellent — above 40 MPG (≤ 5.9 L/100km); good — 30–40 MPG (7.8–5.9 L/100km); average — 20–30 MPG (11.8–7.8 L/100km); poor — below 20 MPG (above 11.8 L/100km). Hybrids and EVs have equivalent ratings of 50–130 MPGe.
MPGe (miles per gallon equivalent) is the EPA's metric for comparing electric vehicles to gasoline cars. It is calculated by converting electrical energy (kWh) to its gallon-equivalent (33.7 kWh = 1 gallon equivalent). A Tesla Model 3 achieves about 130–140 MPGe. This metric helps compare the efficiency of EVs and hybrids on a common scale with gasoline vehicles.
Divide 100 by the L/100km value: $$km/L = \frac{100}{L/100km}$$. For example, 8 L/100km = 100/8 = 12.5 km/L. Conversely: $$L/100km = \frac{100}{km/L}$$. These two metrics are reciprocals of each other — one measures how much fuel you use per distance (consumption), the other measures how far you travel per fuel unit (efficiency).
Yes — at higher altitudes, the air is thinner (lower density), so normally aspirated engines receive less oxygen and burn less fuel, but also produce less power. The net effect on fuel efficiency is complex and depends on driving conditions. In practice, fuel economy at high altitude may decrease by 2–7% because the engine compensates by adjusting fuel mixture, and drivers may use more throttle to maintain speed.
Roboculator Team
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