L/100km to km/L: the simplest fuel conversion there is
What this conversion does
It converts litres per 100 kilometres into kilometres per litre, and nothing else. Both units are metric, so no gallons and no miles appear anywhere in the arithmetic — the whole conversion is 100 divided by the consumption figure. It is the one fuel conversion you can genuinely do in your head.
Why the constant is exactly 100
One unit says "litres burned per 100 km" and the other says "kilometres travelled per litre". Since 100 is the distance both units agree on, kilometres per litre is literally 100 divided by litres per 100 km. There is no physical constant involved and no rounding: 5 L/100km is exactly 20 km/L, and 8 L/100km is exactly 12.5 km/L.
L/100km to km/L conversion table
Consumption figures with their exact kilometres-per-litre equivalent. Because the relationship is a clean reciprocal, every value here is exact rather than approximate.
| Litres per 100 km | Kilometres per litre |
|---|---|
| 2 L/100km | 50.0000 km/L |
| 3 L/100km | 33.3333 km/L |
| 4 L/100km | 25.0000 km/L |
| 5 L/100km | 20.0000 km/L |
| 6 L/100km | 16.6667 km/L |
| 7 L/100km | 14.2857 km/L |
| 8 L/100km | 12.5000 km/L |
| 9 L/100km | 11.1111 km/L |
| 10 L/100km | 10.0000 km/L |
| 12 L/100km | 8.3333 km/L |
| 15 L/100km | 6.6667 km/L |
| 20 L/100km | 5.0000 km/L |
Metres, litres and the reverse scale
The two units run in opposite directions, which catches people out. L/100km falls as a car becomes more efficient; km/L rises. A car quoted at 4 L/100km is 25 km/L and is very economical, while one at 15 L/100km is only 6.67 km/L and is thirsty. Whenever a metric country switches its official label between the two, the number appears to move the wrong way even though the car has not changed.
Using km/L as a quick range estimate
km/L is convenient for trip planning because it multiplies: a 40-litre tank at 15 km/L gives a 600 km range, with no division needed. If you are more used to L/100km, divide 100 by your figure once to get the km/L you can then multiply by tank size.
Frequently asked questions
Why is this conversion exactly 100 and not an approximate constant?
Because the two units describe the same journey in reciprocal terms. Litres per 100 km states fuel for a fixed distance, km/L states distance for a fixed volume, and 100 is the only scaling factor needed. No mile or gallon definition enters the calculation, so no approximation does either.
Which countries use km/L instead of L/100km?
Japan, India and Brazil use km/L on official material, while most of Europe, China and Canada use L/100km. Both are fully metric, so switching between them is a presentation change rather than a measurement one.
Is 20 km/L good?
Yes — 20 km/L is 5.0 L/100km, which puts it among efficient hybrids and small diesels. For reference, 15 km/L is 6.67 L/100km and 25 km/L is 4.0 L/100km. Anything above roughly 25 km/L in a petrol car is exceptional.
Why does the result get smaller when the first number gets bigger?
Because the two units are reciprocals. A larger L/100km figure means the car burns more fuel for the same distance, so it covers fewer kilometres per litre. The result falling is the correct behaviour, not a bug in the calculator.
Can I enter a value with a comma as the decimal point?
Yes. Since both units here are metric and used in comma-decimal countries, the input accepts 7,5 and 7.5 as the same number, rather than truncating at the comma or treating it as a thousands separator.