How do I convert MPG to L/100km?

Use the formula: L/100km = 235.21 / MPG. Example: 25 MPG = 235.21/25 = 9.41 L/100km. Reverse: MPG = 235.21 / (L/100km). The number 235.21 comes from the conversion of miles to km and gallons to liters combined.

What is the difference between US and Imperial MPG?

US MPG uses the US gallon (3.785 L). Imperial MPG uses the UK gallon (4.546 L). A car rated at 30 US MPG = approximately 36 Imperial MPG. European and Canadian efficiency ratings use L/100km. Always check which standard is being used when comparing international vehicle specs.

How much does fuel efficiency matter financially?

Going from 25 MPG to 35 MPG saves about $500-700/year at 12,000 miles/year and $3.50/gallon fuel. The formula: annual savings = (1/old MPG - 1/new MPG) x annual miles x price per gallon. Better fuel efficiency also reduces CO2 emissions proportionally.

What factors affect real-world fuel efficiency?

Real MPG can differ 20-30% from EPA estimates due to: driving style (aggressive acceleration reduces MPG 15-40%), speed (every 5 mph above 50 mph reduces MPG by 7-14%), tire pressure (underinflated tires reduce MPG by 0.2% per PSI), air conditioning (reduces MPG by 5-25%), cold weather (cold engines use 12-30% more fuel), and cargo weight.

Fuel Efficiency - Volume Converter

Convert between m/m³, km/L, mpg (US/UK) and other volumetric fuel efficiency units.

About Fuel Efficiency by Volume

Volumetric fuel efficiency expresses the distance traveled per unit volume of fuel. The SI unit is m/m³. Practical everyday units include km/L and mpg.

Related Converters

Fuel Efficiency Converter • Fuel Efficiency - Mass Converter

Fuel Efficiency by Volume — Global Standards

The US and UK use miles per gallon (mpg), but their gallons differ: 1 US gallon = 3.785 L, 1 UK gallon = 4.546 L. The EU mandates L/100km for vehicle labelling. A car rated at 6 L/100km is approximately 47 US mpg or 39 UK mpg. Always check which standard is being used when comparing specs from different regions.

Fuel Efficiency Conversion Table

L/100km	US mpg	UK mpg	km/L
4.0	58.8	70.6	25.0
6.0	39.2	47.1	16.7
8.0	29.4	35.3	12.5

Key Fuel Volume Unit Differences

When calculating fuel economy across countries, the gallon difference matters. A US gallon (3.785 L) and a UK imperial gallon (4.546 L) differ by 20%. A car rated 40 mpg in UK tests uses approximately 7.06 L/100km; a 40 mpg US rating uses 5.88 L/100km. Japan uses km/L (inverse of L/100km): 15 km/L = 6.67 L/100km = 35.3 US mpg. When reading an electric vehicle's energy equivalent, 33.7 kWh equals 1 US gallon of gasoline for MPGe calculations.

Converting Fuel Consumption Units

Fuel consumption per volume expresses how much fuel is used per unit distance. The metric system uses litres per 100 kilometres (L/100km); the US uses miles per gallon (mpg); the UK uses miles per imperial gallon. Additional units: kilometres per litre (km/L), commonly used in Asia. Conversion formulas: L/100km = 235.215 / mpg (US); km/L = 100 / (L/100km); mpg (UK) = mpg (US) × 1.20095 (since 1 UK gallon = 1.20095 US gallons).

Fuel consumption standards and regulations worldwide use L/100km or grams CO₂ per kilometre. The EU mandatory CO₂ targets for new cars (95 g/km fleet average corresponds to approximately 4.1 L/100km petrol). When comparing new car specs across markets, converting to a common unit — preferably L/100km for the absolute fuel quantity, or mpg for intuitive economy — avoids misinterpretation.

Volume Fuel Efficiency Conversions

L/100km	km/L	mpg US	mpg UK
4.0	25.0	58.8	70.6
6.0	16.7	39.2	47.1
8.0	12.5	29.4	35.3
10.0	10.0	23.5	28.2
12.0	8.3	19.6	23.5

Volume-Based Fuel Efficiency Across Different Gallons

Fuel efficiency measured in distance per volume unit (miles per gallon, km per liter) depends entirely on which gallon or liter standard is being used. The US gallon (3.785 L) and imperial gallon (4.546 L) differ by about 20%, which means a car rated at 30 MPG US would achieve approximately 36 MPG on the imperial scale — a significant apparent difference for the same vehicle. This confusion regularly affects consumers comparing American and British car reviews. To convert MPG US to MPG imperial, multiply by 1.20095. To convert MPG US to L/100km, use 235.215 / MPG. For km/L, divide MPG US by 2.35215. Fleet procurement teams evaluating vehicles from multiple countries must standardize all fuel efficiency figures to one base before comparing total cost of ownership. Fuel cost calculators for international travel also require consistent units when estimating expenses per kilometer of trip distance.

Volume-Based Efficiency Reference Table

MPG (US)	MPG (Imperial)	L/100km	km/L
20	24.0	11.76	8.50
25	30.0	9.41	10.63
30	36.0	7.84	12.75
40	48.0	5.88	17.00
50	60.0	4.70	21.26