The complete fuel economy converter
This free fuel economy converter turns mileage figures between MPG (US & UK), km/L, L/100km and a dozen more units — correctly handling the fact that some units improve as the number goes up (MPG, km/L) while others improve as it goes down (L/100km). Beyond conversion it calculates fuel cost, trips, fleet expenses, CO₂ emissions and EV efficiency, and benchmarks your mileage by vehicle type — all in your browser.
16 units + EV
MPG (US/UK), km/L, L/100km, mi/L, nautical and EV units — all interconvert correctly.
Multi-unit output
Type one value and see it in every unit at once, plus formulas and step-by-step working.
Cost & trip tools
Fuel cost, trip planning, refuelling stops, price impact and fleet calculators.
CO₂ emissions
Estimate trip, monthly and annual CO₂ by fuel type — petrol, diesel, LPG and more.
EV efficiency
Convert kWh/100km, Wh/km, mi/kWh and km/kWh, and estimate charging cost.
100% private
Every calculation runs in your browser. History and favorites stay on your device.
Quick answers
What is 30 MPG in km/L?
30 MPG (US) = 12.75 km/L.
What is 30 MPG in L/100km?
30 MPG (US) = 7.84 L/100km.
Which is better: higher MPG or lower L/100km?
Higher MPG and lower L/100km both indicate better fuel efficiency.
What is the difference between MPG US and MPG UK?
A UK gallon is ~20% larger than a US gallon, so 30 MPG (US) ≈ 36 MPG (UK).
How do I convert MPG to L/100km?
L/100km (US) = 235.215 ÷ MPG. They are inverse units.
How is EV efficiency measured?
In kWh/100km or Wh/km (lower is better) and miles/kWh or km/kWh (higher is better).
Typical fuel economy by vehicle
| Vehicle | MPG (US) | km/L | L/100km |
|---|---|---|---|
| Compact car | 38 | 16.2 | 6.2 |
| Sedan | 32 | 13.6 | 7.4 |
| SUV | 24 | 10.2 | 9.8 |
| Pickup truck | 19 | 8.1 | 12.4 |
| Motorcycle | 55 | 23.4 | 4.3 |
| Hybrid | 52 | 22.1 | 4.5 |
| EV (gas equivalent) | 110 | 46.8 | 2.1 |
Understanding fuel economy
What is fuel economy?
Fuel economy is the relationship between the distance a vehicle travels and the fuel it consumes. It is the single most important number for running cost and emissions, and it is reported either as distance per unit of fuel (MPG, km/L — higher is better) or fuel per unit of distance (L/100km — lower is better).
How is fuel efficiency measured?
Manufacturers measure economy under standardized test cycles, then express it in a regional unit: MPG in the US and UK, km/L in much of Asia, and L/100km across Europe. Because these units describe the same physics from different angles, a converter is needed to compare cars sold in different markets.
Difference between MPG (US) and MPG (UK)
Both count miles per gallon, but the gallon differs: a US gallon is 3.785 litres while a UK imperial gallon is 4.546 litres. The UK gallon is about 20% larger, so a vehicle covers more miles per UK gallon. As a result UK MPG numbers look higher than US numbers for the same real efficiency — 50 MPG (UK) is only about 42 MPG (US).
How EV efficiency is measured
Electric vehicles store energy in kilowatt-hours rather than litres of fuel, so efficiency is measured in energy per distance — kWh/100km or Wh/km (lower is better) — or distance per energy — miles/kWh or km/kWh (higher is better). To compare an EV with a petrol car, energy use is sometimes converted to a "miles per gallon equivalent" (MPGe).
How fuel costs affect ownership
Fuel is typically the largest variable cost of running a vehicle. A car doing 10 km/L versus 15 km/L over 15,000 km a year burns 500 extra litres — a substantial annual sum that compounds over years of ownership. Higher efficiency lowers running cost, reduces CO₂ emissions, and often improves resale value as fuel prices climb.
Accuracy & method
Every conversion reduces the value to a single physical quantity — litres of fuel per metre travelled — using exact unit definitions (1 mile = 1609.344 m, 1 US gallon = 3.785411784 L, 1 UK gallon = 4.54609 L). This guarantees that distance-per-fuel units (MPG, km/L) and fuel-per-distance units (L/100km) convert correctly in both directions, even though they are inversely related. Emissions use standard CO₂ factors per litre, and figures are estimates for guidance.
Frequently asked questions
What is fuel economy?
Fuel economy measures how far a vehicle travels on a given amount of fuel. It is expressed either as distance per fuel (higher is better, like MPG or km/L) or fuel per distance (lower is better, like L/100km).
What is MPG?
MPG means miles per gallon — the number of miles a vehicle can travel on one gallon of fuel. A higher MPG means better efficiency. Note that US and UK (imperial) gallons differ, so MPG figures are not directly comparable between them.
What is km/L?
km/L means kilometres per litre — how many kilometres a vehicle travels on one litre of fuel. It is the metric equivalent of MPG, and a higher number means better efficiency.
What is L/100km?
L/100km means litres of fuel used to travel 100 kilometres. Unlike MPG and km/L, a lower L/100km value means better efficiency. It is the standard fuel-economy unit across most of Europe.
What is 30 MPG in km/L?
30 MPG (US) equals about 12.75 km/L. You can also express it as roughly 7.84 L/100km.
What is the difference between MPG US and MPG UK?
The difference is the gallon. A US gallon is 3.785 litres while a UK (imperial) gallon is 4.546 litres — about 20% larger. So the same car shows a higher MPG figure in UK gallons: 30 MPG (US) equals about 36 MPG (UK).
Which is better: higher MPG or lower L/100km?
Both indicate better fuel efficiency. MPG and km/L measure distance per fuel, so higher is better. L/100km measures fuel per distance, so lower is better. They describe the same thing from opposite directions.
How do I convert MPG to L/100km?
Because they are inverse units, you divide rather than multiply: L/100km (US) = 235.215 ÷ MPG(US). For example, 30 MPG = 235.215 ÷ 30 ≈ 7.84 L/100km.
How do I convert L/100km to MPG?
Use MPG (US) = 235.215 ÷ L/100km. For example, 8 L/100km = 235.215 ÷ 8 ≈ 29.4 MPG (US).
How do I convert MPG to km/L?
Multiply by 0.425144: km/L = MPG(US) × 0.425144. For example, 30 × 0.425144 ≈ 12.75 km/L.
How do I convert km/L to L/100km?
Divide 100 by the km/L value: L/100km = 100 ÷ km/L. For example, 20 km/L = 100 ÷ 20 = 5 L/100km.
How do I calculate fuel cost for a trip?
Divide the distance by your fuel economy to get the fuel needed, then multiply by the fuel price. Fuel needed = distance ÷ economy; cost = fuel needed × price. The Fuel Cost calculator does this automatically.
How accurate is this fuel economy converter?
Conversions use exact unit definitions (1 mile = 1609.344 m, 1 US gallon = 3.785411784 L, 1 UK gallon = 4.54609 L) and are computed to high precision, with adjustable decimal places.
Why are US and UK MPG figures different?
They use different sized gallons. A UK imperial gallon (4.546 L) is about 20% larger than a US gallon (3.785 L), so a car covers more miles per UK gallon — making UK MPG numbers look higher for the same real efficiency.
How is EV efficiency measured?
Electric vehicles use energy rather than fuel volume. Common units are kWh/100km and Wh/km (energy per distance, lower is better) and miles/kWh or km/kWh (distance per energy, higher is better). The EV module converts between them.
What is a good fuel economy?
It depends on the vehicle. For a sedan, around 14–18 km/L (33–42 MPG US) is good; an SUV around 10–13 km/L is good; a motorcycle 35–45 km/L. The Benchmarks tool rates your figure by vehicle category.
How do hybrids compare to petrol cars?
Hybrids typically achieve 40–60% better fuel economy in city driving by recovering braking energy and using the electric motor at low speeds. They burn the same petrol but use less of it, lowering both cost and emissions.
How do I calculate CO₂ emissions from fuel?
Burning one litre of petrol releases about 2.31 kg of CO₂, and diesel about 2.68 kg. Multiply the litres used (distance ÷ economy) by the fuel’s emission factor. The Emissions tool calculates monthly and annual totals.
What is the most efficient fuel economy unit?
No unit is more accurate — they all describe the same physics. L/100km is preferred in science and most of the world because it scales linearly with fuel use, making cost and emissions easy to calculate.
How much can better fuel economy save me?
Savings depend on distance and fuel price. Improving from 12 to 16 km/L over 15,000 km a year saves about 312 litres annually — use the Compare & Save tool to see the figure for your numbers.
What is km/gal?
km/gal expresses kilometres travelled per gallon of fuel. Because gallons come in US and UK sizes, this tool supports both km/gal (US) and km/gal (UK).
Does fuel economy change with driving style?
Yes, significantly. Aggressive acceleration, high speeds, idling, under-inflated tyres and roof racks all reduce economy. Smooth, steady driving can improve real-world mileage by 15–30%.
How do I plan fuel for a road trip?
Enter the trip distance, your vehicle’s economy and the fuel price into the Trip planner. It returns total fuel needed, total cost and the number of refuelling stops based on your tank size, for one-way or round trips.
What is nautical miles per gallon?
Nautical miles per gallon (nmi/gal) measures efficiency for boats and ships, where a nautical mile is 1,852 metres. This tool converts it to and from road units.
Can I compare two vehicles?
Yes. The Compare & Save tool takes two vehicles’ fuel economy, your annual distance and the fuel price, and shows the fuel and money each uses plus your yearly savings by choosing the more efficient one.
How is fleet fuel cost calculated?
Multiply each vehicle’s consumption by the number of vehicles and the distance driven, then by the fuel price. The Fleet tool totals monthly and annual fuel cost for a group of vehicles.
Does fuel economy affect resale and ownership cost?
Yes. Fuel is one of the largest running costs of a vehicle, so a more efficient model can save thousands over its life. Efficient vehicles also tend to hold value better as fuel prices rise.
Is the converter free and private?
Yes. It is completely free with no sign-up, and every calculation runs in your browser — your data is never uploaded. It also works offline once loaded.
Can I save my conversions and vehicles?
Yes. Recent conversions are kept in history, and you can star favorite conversions and vehicles — all stored locally in your browser.
How do I convert between US and metric units quickly?
Type any value and the multi-unit output instantly shows it in every supported unit — MPG (US/UK), km/L, L/100km, mi/L and more — so you never need to convert one at a time.
What does a fuel-price increase cost me?
Multiply your annual fuel use by the price difference. For example, at 1,200 litres a year, a 10-currency-unit-per-litre rise costs 12,000 more annually. The Fuel Cost tool models price changes for you.
How many MPG is good for an SUV?
For an SUV, roughly 24 MPG (US) / 10 km/L is average, 30 MPG / 13 km/L is good and 38+ MPG / 16+ km/L is excellent. Hybrids and smaller crossovers reach the higher end.
Why does the converter use exact definitions?
Using the internationally agreed values for the mile, US gallon and UK gallon means results match official figures and other reliable references, rather than rounded approximations.
Can I export my results?
Yes. You can copy and share results, print the page, and download conversions as TXT, CSV or PDF for records, reports or sharing with a fleet.
Does the tool work on mobile?
Yes, it is mobile-first and fully responsive, with touch-friendly inputs and accessible controls, and it works offline once the page has loaded.
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