Fuel Economy Converter
Convert fuel economy between US MPG, UK MPG, liters per 100km, and km per liter. Compare two vehicles, estimate annual fuel cost, and calculate CO2 emissions.
Converted Value
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Result
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MPG US
mi
$/gal
Annual Cost & Savings
Annual Fuel Cost —
Annual Savings vs Old Car —
Emissions
CO₂ Emissions —
Annual CO₂ —
Electric Equivalent
Equiv. EV Efficiency —
How to Use This Calculator
- Enter your fuel economy value and select the From Unit (MPG US, MPG UK, L/100km, or km/L).
- Select the To Unit to see the converted result.
- Use All Units to see all four representations at once.
- Use Compare Vehicles to estimate and compare annual fuel costs for two vehicles.
- The Professional tab adds CO2 emissions, electric equivalent efficiency, and fuel savings.
Formula
L/100km = 235.214 / MPG(US) | km/L = 100 / L/100km
MPG(UK) = MPG(US) × 1.20095 (UK gallon is 20% larger)
Annual cost ($) = (Distance ÷ MPG) × price/gallon
Example
Convert 30 MPG US: L/100km = 235.214/30 = 7.84 L/100km | km/L = 100/7.84 = 12.75 km/L | MPG UK = 30 × 1.20095 = 36.03 MPG UK.
Frequently Asked Questions
- L/100km = 235.214 / MPG (US). So 30 MPG US = 235.214/30 = 7.84 L/100km. Note: lower L/100km means more efficient; higher MPG means more efficient.
- A US gallon = 3.785 liters. A UK (imperial) gallon = 4.546 liters. So UK MPG is always about 20% higher than US MPG for the same car. 40 UK MPG ≈ 33.3 US MPG.
- km/L = 100 / (L/100km). So 8 L/100km = 100/8 = 12.5 km/L. This is useful in countries like Japan and Israel that use km/L.
- Burning 1 liter of petrol (gasoline) produces approximately 2.31 kg of CO2. For diesel: approximately 2.68 kg/L. CO2 emissions in g/km = (L/100km × 2310) / 100.
- For a regular car: 35+ MPG US (6.7 L/100km) is good, 50+ MPG is excellent. Hybrids often achieve 50–60 MPG. The average US car gets about 28 MPG.