km Per Litre To Litres Per 100 km Converter
Convert kilometres per litre into L/100km, UK MPG, US MPG and fuel cost so economy figures from different countries can be compared correctly.
Convert km/L To L/100km
Fuel Economy Result
6.67 L/100km
15 km/L is 6.67 litres per 100 km.
L/100km is an inverse measure: lower is better. Do not average L/100km and km/L as if they were the same scale.
Formula And Gallon Notes
L/100km = 100 / km per litreUK MPG = km per litre x 2.824809363US MPG = km per litre x 2.352145833fuel cost per 100 km = L/100km x price per litreThe L/100km formula is an inverse calculation. A car that travels farther on each litre uses fewer litres for 100 km. This is why improving from 10 km/L to 20 km/L does not add a fixed number to L/100km; it halves the fuel used per 100 km from 10.0 to 5.0.
UK MPG and US MPG are not the same because an imperial gallon is larger than a US gallon. When comparing overseas reviews, auction sheets or import listings, check which gallon system is being used before treating an MPG figure as familiar.
Common Economy Table
| km/L | L/100km | UK MPG | Cost Per 100 km At GBP 1.45/L |
|---|---|---|---|
| 8 | 12.50 | 22.60 | GBP 18.13 |
| 10 | 10.00 | 28.25 | GBP 14.50 |
| 15 | 6.67 | 42.37 | GBP 9.67 |
| 20 | 5.00 | 56.50 | GBP 7.25 |
| 25 | 4.00 | 70.62 | GBP 5.80 |
Import, Trip And Running-Cost Checks
Japanese Import Sheets
Japan often uses km/L. UK drivers may be more familiar with MPG or L/100km. Convert first, then remember that test cycles, tyres, air conditioning, load and driving pattern can change real fuel use.
Fleet Fuel Notes
L/100km is useful for cost control because it links directly to litres used over distance. If two vehicles cover the same mileage, the lower L/100km value uses less fuel.
Hybrid And Diesel Comparisons
Short urban runs, cold starts, battery state and motorway speed can move real economy far from a brochure or import figure. Use the calculator for unit comparison, then check real fill-to-fill records.
Worked Examples
A car listed at 18 km/L converts to 5.56 L/100km and 50.85 UK MPG. At GBP 1.45 per litre, that is about GBP 8.06 per 100 km. If the car covers 12,000 km per year, estimated fuel use is about 667 litres, costing roughly GBP 967 at that price.
A less efficient vehicle at 9 km/L converts to 11.11 L/100km and 25.42 UK MPG. The cost per 100 km at GBP 1.45 per litre is GBP 16.11. The difference between the two vehicles is clearer in annual litres than in headline MPG because distance and fuel price are visible.
Using Fill-To-Fill Records
The best way to check a converted economy figure is to compare it with fill-to-fill records. Fill the tank, reset the trip meter, drive normally, then fill again and record litres added and distance covered. Divide kilometres by litres to get km/L, or divide litres by kilometres and multiply by 100 to get L/100km. Repeat over several tanks because one fill can be affected by pump cut-off, slope, weather, traffic and short trips.
For imported vehicles, the quoted km/L figure may come from a test cycle that does not match UK use. Tyres, roof bars, air conditioning, motorway speed, winter fuel, towing and load can all increase real litres per 100 km. If you are budgeting, run a cautious case with a worse economy figure as well as the advertised one.
For comparison shopping, L/100km can be easier than MPG because each point is a direct fuel amount. A change from 10 L/100km to 8 L/100km saves 2 litres every 100 km. Over 12,000 km, that is 240 litres. Multiplying by the pump price gives the annual cash difference without any extra unit step.
If you track fuel in miles but the source figure is km/L, convert distance first or use one system consistently. Mixing miles, kilometres, litres and gallons in the same notebook is a common source of false economy claims. Keep the raw receipt litres and odometer distance so you can recalculate later.
For shared cars or fleet vehicles, separate driver behaviour from vehicle condition. A sudden change in L/100km can come from tyres, dragging brakes, roof load, route mix or fuel quality as well as driving style. Service records can explain a change, especially after tyre, brake, oil or sensor work. Note the season too.
FAQ
How do I convert km/L to L/100km?
Divide 100 by the km/L figure. For example, 20 km/L becomes 5 L/100km.
Is a higher km/L better?
Yes. Higher km/L means the vehicle travels farther on each litre. For L/100km, lower is better.
Why include UK and US MPG?
UK gallons and US gallons are different sizes. A single MPG number is ambiguous unless the gallon system is stated.
Can I use this for real fuel bills?
It can estimate cost from a stated economy and fuel price. Real bills depend on traffic, load, servicing, weather, tyre pressure and driving style.
Can I average two km/L readings?
For best accuracy, total the distance and fuel used, then calculate one combined km/L. Simple averages can mislead if the distances differ.
Does this work for EVs?
No. EV economy usually uses kWh per mile, miles per kWh or kWh per 100 km. This page is for liquid fuel measured in litres.
Sources
- International Bureau of Weights and Measures. (2019). The International System of Units (SI), 9th edition. BIPM. https://www.bipm.org/en/publications/si-brochure
- National Institute of Standards and Technology. (2008). Guide for the use of the International System of Units (SI), Special Publication 811. NIST. https://www.nist.gov/pml/special-publication-811
- GOV.UK. (n.d.). Fuel consumption and CO2. GOV.UK. https://www.gov.uk/co2-and-vehicle-tax-tools