Kilometers per Liter Fuel Economy Calculator

What kilometers per liter measures

Kilometers per liter is distance divided by fuel. A car that travels 15 km on one liter of gasoline returns 15 km/L. The unit is common in India, Japan, Brazil and parts of Asia, and it reads the same way as miles per gallon: bigger is better, and the number tells you how far a fixed amount of fuel takes you.

To get it, divide the distance driven by the fuel added. A 450 km trip that takes 30 liters is 450 divided by 30, which is 15 km/L. Fill the tank to the same point both times and the number is accurate to within a few percent.

The unit is not used on US window stickers, which show miles per gallon, and it is not used in most of Europe, which shows liters per 100 km. That makes it the odd one out among the three common measures, and it is the one most likely to need converting.

km/L and L/100km are reciprocals

The two metric measures are inverses of each other, with a factor of 100 to keep the numbers readable. Liters per 100 km equals 100 divided by km per liter, and km per liter equals 100 divided by liters per 100 km. Nothing else changes, and there is no offset or correction term.

That relationship makes the conversion exact and reversible. 15 km/L is 100 divided by 15, which is 6.67 L/100km. Convert back and 100 divided by 6.67 is 14.99, which rounds to 15. A 20 km/L car is 5.00 L/100km, and 5.00 L/100km is 20.00 km/L.

Because the relation is a reciprocal, the pairs are not evenly spaced. The gap from 5 to 6 km/L is 3.33 liters per 100 km, while the gap from 25 to 26 km/L is only 0.15 liters. Small improvements at the efficient end of the scale look tiny in liters and huge in km/L.

The table reads in both directions. Pick a row by km/L and read the L/100km cell, or pick a row by MPG and work back to the metric pair. Rows are spaced to cover the range of real vehicles, from a heavy truck at the bottom to a small hybrid at the top.

Why bigger is better in one unit and worse in the other

The direction flips because the denominator moves. In km per liter the fuel is the denominator, so more kilometers on the same liter is an improvement. In liters per 100 km the distance is the denominator, so fewer liters for the same 100 km is an improvement.

This is the same trap the US EPA describes on its fuel economy label page, where it calls the miles per gallon illusion out directly: a jump from 10 to 15 MPG saves far more fuel than a jump from 30 to 35 MPG, even though both look like 5 MPG. The same arithmetic applies in metric, and it is the reason a consumption figure is a better shopping tool than an economy figure.

Read a km/L number as distance and a L/100km number as cost. A car that goes from 10 to 12 km/L uses 16.7 percent less fuel, and a car that goes from 8.33 to 10 L/100km uses the same 16.7 percent less. Same car, same saving, two different looking numbers.

Converting km/L to US MPG

The conversion needs two exact definitions. A US gallon is 3.785411784 liters and an international mile is 1.609344 km, both of which appear in the NIST Handbook 133 tables of units. Divide the gallon by the mile and the factor is 2.3521458, so US MPG equals km/L times 2.352.

Going the other way, km/L equals US MPG times 0.425144, because 1.609344 divided by 3.785411784 is 0.425144. A 30 MPG car is 30 times 0.425144, which is 12.75 km/L, and 12.75 km/L converts back to 29.99 MPG.

The imperial gallon changes the factor, not the method. At 4.54609 liters, the UK factor is 2.824809, so the same car reads 20.1 percent higher in UK MPG than in US MPG. A car at 35.3 US MPG is 42.4 UK MPG, and a car advertised at 50 UK MPG is 41.6 US MPG.

Worked example: 15 km/L in every unit

Start with 15 km per liter and convert it three ways. Every step is written out so you can follow it with a calculator.

• Liters per 100 km: 100 divided by 15 is 6.67 L/100km.
• US MPG: 15 times 3.785411784 is 56.781, and 56.781 divided by 1.609344 is 35.28 US MPG.
• UK MPG: 15 times 4.54609 is 68.191, and 68.191 divided by 1.609344 is 42.37 UK MPG.
• Fuel for 500 km: 500 divided by 15 is 33.33 liters, which is 8.81 US gallons.
• Cost at $0.95 per liter: 33.33 times 0.95 is $31.67, or 6.3 cents per km.

The same car at 20 km/L would use 25.00 liters for the same 500 km, a saving of 8.33 liters and about $7.92. That is the kind of difference a fuel economy comparison is meant to catch, and it is invisible if you only look at the km/L figures of 15 and 20.

Fuel used and cost over a distance

Fuel used is distance divided by km per liter. Cost is that fuel multiplied by the price per liter. Both are linear in distance, so a 1,000 km trip uses exactly twice the fuel of a 500 km trip at the same economy.

The cost per 100 km is the number worth memorizing. At 15 km/L and $0.95 a liter it is $6.33 per 100 km, or 6.3 cents per km. Change the price to $1.20 and the same car costs $8.00 per 100 km, a 26 percent jump from a 26 percent jump in the pump price.

This is why the L/100km form is convenient for budgeting: the figure is already normalized to a distance, so multiplying by the number of hundreds of kilometers gives the fuel, and one more multiplication gives the money. The km/L form needs a division first.

US gallons, imperial gallons and the 20 percent gap

Two gallons share a name and not a size. The US liquid gallon is 231 cubic inches, or 3.785411784 liters, while the imperial gallon used in the UK and some Commonwealth countries is 4.54609 liters. The imperial gallon is 20.1 percent larger, so the same car returns 20.1 percent more miles per imperial gallon.

That gap explains a persistent confusion in car reviews. A UK magazine quoting 50 MPG is describing 41.6 US MPG, not 50. A US window sticker quoting 30 MPG is 36.0 UK MPG. Neither number is wrong; they are measured against different gallons.

Canada and Ireland switched to liters per 100 km decades ago, which removed the ambiguity. If you are converting an older figure and the source does not say which gallon, check the country: a UK source means imperial, a US source means US liquid.

Reading a metric figure on a US road trip

If you rent a car in a country that quotes km/L or L/100km, the conversion matters at the pump. A car rated at 6.0 L/100km uses 16.67 km/L, which is 39.2 US MPG, so a 400 km drive burns 24 liters. A car rated at 12.0 L/100km is 8.33 km/L and 19.6 US MPG, and the same drive burns 48 liters.

The trip computer in most rental cars can switch units, and the switch is usually in a settings menu rather than on the dash. If it cannot, remember one anchor: 10 km/L is 23.5 US MPG and 10 L/100km, which is an easy pair to hold in your head for a rough check.

For a quick estimate on the road, divide the distance in km by the km/L figure to get liters, then multiply by the local price. That is the same arithmetic the calculator above runs, and it takes about as long as reading the pump display.

Fuel economy figures are estimates. Real consumption depends on speed, load, tire pressure, temperature and driving style, and a car that returns 15 km/L on a steady highway run can return 11 km/L in city traffic.