Fuel Efficiency Converter
Convert between km/L, L/100km, miles per gallon (US and UK), and other fuel economy units.
About the Fuel Efficiency Converter
Fuel efficiency is one of the most practical metrics for vehicle ownership decisions, yet it is expressed differently across regions in ways that make direct comparison difficult. India and most of Asia rate vehicles in kilometers per liter (km/L). Europe uses liters per 100 km (L/100km). The US and UK use miles per gallon (MPG), with the US and UK gallon being different sizes. An Indian car claiming 20 km/L, a European vehicle rated at 5.5 L/100km, and a US car at 45 MPG all represent similar efficiency levels - but arriving at that conclusion requires accurate cross-unit conversion.
The directional difference adds a layer of confusion: higher km/L means better efficiency, while lower L/100km also means better efficiency. These two scales are inverses of each other (L/100km = 100 / km/L). When evaluating imported vehicle specifications or comparing EV and petrol options using international efficiency ratings, understanding this inverse relationship prevents the common error of treating higher numbers as better across all scales.
Beyond simple comparisons, fuel efficiency conversion is essential for practical running cost calculations. A car doing 18 km/L at Rs. 105/liter of petrol costs Rs. 5.83/km. The same car rated as 23.8 MPG in the US at USD 1.25/liter costs approximately Rs. 3.67/km equivalent at current exchange rates. Understanding both the unit conversion and the cost-per-km calculation together makes it possible to compare vehicle running costs across markets and fuel types, including petrol, diesel, CNG, and electric.
Fuel Efficiency Conversion
km/L to L/100km: L/100km = 100 / km/L · km/L to MPG (US): MPG = km/L x 2.352
1 US gallon = 3.785 liters · 1 UK Imperial gallon = 4.546 liters · MPG (UK) = km/L x 2.825 · Average Indian car: 15-20 km/L city, 18-25 km/L highway · EV: typically 5-8 km/kWh
Worked Example
Indian car claims 18 km/L ARAI - what is this in L/100km and US MPG?
18 km/L = 5.56 L/100km = 42.3 US MPG · Real-world estimate at 75% ARAI: 13.5 km/L
Tips & Insights
- 1
ARAI-certified fuel efficiency in India is tested under controlled conditions and typically runs 20-30% higher than real-world city driving figures. For budget planning, use 70-80% of the ARAI figure. A car rated 22 km/L ARAI will likely return 15-18 km/L in city traffic.
- 2
L/100km and km/L are inverse measures: km/L = 100 / L/100km. A car rated 6 L/100km = 16.7 km/L. A 1 L/100km improvement from 8 to 7 L/100km is a bigger efficiency gain than a 1 km/L improvement from 8 to 9 km/L because the relationship is non-linear.
- 3
US vs UK MPG: 1 US gallon = 3.785 L; 1 UK Imperial gallon = 4.546 L. A car rated 40 MPG (US) = 33.3 MPG (UK) for the same vehicle. UK MPG figures always appear higher than US MPG because the gallon is larger. Never compare US and UK MPG figures directly.
- 4
EV efficiency in km/kWh: at Rs. 7/kWh electricity and 6 km/kWh EV efficiency, the energy cost is Rs. 1.17/km. Compare with petrol at Rs. 105/liter and 15 km/L: Rs. 7/km. The EV is about 83% cheaper on fuel alone - this calculation makes the economic case for EVs concrete.
- 5
CNG vehicles are rated in km/kg. CNG at approximately Rs. 90/kg and 25 km/kg = Rs. 3.6/km running cost. Compare with the petrol version of the same vehicle at Rs. 105/liter and 15 km/L = Rs. 7/km. CNG is about 49% cheaper per km on fuel cost alone.
- 6
Tyres, AC usage, and driving speed significantly affect real-world fuel efficiency. Highway driving at 80-90 km/h typically gives 10-15% better fuel economy than at 110-120 km/h due to aerodynamic drag. AC adds a 0.5-1.5 km/L penalty in city driving. These real-world factors matter as much as the ARAI rating.
- 7
For fleet operators and logistics companies, L/100km is the preferred metric because it scales linearly with fuel cost. If 10 trucks each cover 500 km/day at 8 L/100km, the daily fuel bill = 10 x 500 x 0.08 x price/liter. This calculation is straightforward in L/100km but awkward to set up in km/L form.
Why this matters for you
Vehicle purchase is typically the second-largest financial decision in an Indian household after housing. Over a 5-7 year ownership period, fuel cost can exceed the vehicle purchase price for high-mileage users. A car that delivers 15 km/L instead of 20 km/L costs Rs. 1,750 more per 1,000 km at Rs. 105/liter petrol - approximately Rs. 7,000-10,000 extra annually for an average Indian driver. Understanding fuel efficiency numbers accurately, and converting them to a consistent per-km cost, makes this long-term cost difference visible at the point of purchase.
India's vehicle market is at a transitional moment as EVs and CNG alternatives become commercially viable for mainstream buyers. Comparing EV km/kWh against petrol km/L and CNG km/kg requires conversion to a common unit - cost per km is the most practical choice. Without this conversion, the comparison feels like comparing apples and oranges. With it, the decision becomes a straightforward financial calculation that can be updated every time fuel prices or electricity tariffs change.
For automotive enthusiasts, policy researchers, and automotive journalists comparing global vehicles, fuel efficiency unit conversion is essential for fair international comparisons. An Indian SUV at 14 km/L, a European equivalent at 7 L/100km, and a US competitor at 35 MPG are all broadly similar in efficiency - but this is not obvious from the raw numbers without conversion. Building intuition for efficiency across all three major unit systems supports better-informed vehicle assessments and purchasing decisions in an increasingly global automotive marketplace.
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Frequently Asked Questions
How do I convert km/L to L/100km?+
L/100km = 100 ÷ km/L. For example, 15 km/L = 100÷15 = 6.67 L/100km. These units are inversely related - higher km/L = lower L/100km = better fuel economy.
How do I convert km/L to mpg?+
US mpg = km/L × 2.35215. For example, 15 km/L × 2.35215 = 35.3 mpg (US). UK (Imperial) mpg = km/L × 2.82481. Note: US and UK gallons are different sizes.
What is the difference between US and UK gallon?+
1 US gallon = 3.78541 liters. 1 UK (Imperial) gallon = 4.54609 liters. A car rated at 40 mpg (US) = 33.3 mpg (UK) - always specify which gallon when comparing.
What is a good fuel efficiency for a car?+
For petrol cars: excellent = 20+ km/L, good = 15–20 km/L, average = 10–15 km/L. For diesel: 5–8 km/L more. EVs are measured in km/kWh (typically 5–8 km/kWh) - equivalent to ~50–80 km/L in energy terms.
What is a good mileage figure for Indian vehicles?+
ARAI certified mileage versus real-world figures (typically 20-30% lower): Hatchbacks - ARAI 20-25 km/L, real-world 15-20 km/L. Sedans - ARAI 18-22 km/L, real-world 14-18 km/L. SUVs - ARAI 15-20 km/L, real-world 12-16 km/L. Electric vehicles - MIDC certified 200-600 km range, real-world 150-450 km. Factors reducing real-world mileage: AC use reduces mileage by 15-20%, city traffic versus highway, driving habits, and tyre pressure. The best way to measure your actual efficiency: fill up, drive 400 or more km, fill up again, then divide distance by fuel used.
How do I measure my vehicle's actual real-world fuel efficiency?+
The most accurate method: fill your tank completely. Drive your normal mix of city and highway. Fill the tank again and note the exact litres added and the exact distance driven since the last fill. Fuel efficiency = Distance / Litres added. For example, if you added 32 litres after driving 400 km: efficiency = 400 / 32 = 12.5 km/L. This method accounts for all real-world factors (AC use, traffic, driving style, road conditions) that ARAI's certified test cannot replicate. Conduct the test over at least 200 to 300 km for meaningful results. Common findings: city driving is 30 to 50% less efficient than highway driving for the same vehicle. Running the AC continuously in Indian summer reduces efficiency by 15 to 25%. Tyre pressure 10% below spec reduces efficiency by 3 to 4%. Aggressive acceleration and braking reduces efficiency by 20 to 30% compared to smooth, anticipatory driving.
How does EV range compare to petrol vehicle range in India?+
Comparing EV and petrol vehicle range requires understanding different efficiency metrics. Petrol vehicles use km/L; EVs use km/kWh. A typical Indian petrol hatchback achieves 15 to 18 km/L real-world. A typical Indian EV (Tata Nexon EV, MG ZS EV) achieves 5 to 7 km/kWh real-world. With 40 kWh battery, real range is 200 to 280 km. Running cost comparison: Petrol at Rs. 105/L and 15 km/L = Rs. 7 per km. Electricity at Rs. 8/kWh and 6 km/kWh = Rs. 1.33 per km. EVs save approximately Rs. 5.67 per km, or Rs. 5,670 per 1,000 km. Over 15,000 km annual driving, an EV saves approximately Rs. 85,050 per year in fuel. The premium for an EV (typically Rs. 5 to 10 lakh above equivalent petrol car) has a payback period of roughly 6 to 12 years at current prices and driving patterns.