How this converter works
The converter answers one question first: what does this MPG figure mean in liters per 100 kilometers? Enter the number, pick the direction, and check the gallon type before you read the result. The gallon selector sits in the open on purpose. A UK gallon holds 4.54609 liters, and a US gallon holds 3.785411784 liters, so the same MPG number produces two different answers, and a hidden default picks one of them without telling you.
Two constants do all the work on this page. For a UK gallon, L/100km equals 282.481 divided by MPG. For a US gallon, L/100km equals 235.215 divided by MPG. The reverse trip uses the same constant in the other direction: MPG equals the constant divided by the L/100km figure. The page also shows a km/L readout, because Japanese auction sheets quote kilometers per liter, and km/L equals 100 divided by the L/100km result.
L/100km runs in the opposite direction to MPG, and that trips many readers. MPG measures distance per unit of fuel, so higher reads better. L/100km measures fuel per fixed distance, so lower reads better. A car at 5 L/100km drinks less than a car at 9 L/100km, even though 9 is the bigger number on the page.
MPG to L/100km conversion table
The table below converts MPG figures from 15 to 70 into L/100km, with one column per gallon type, so a reader can compare a US review and a UK brochure on the same line.
| MPG | L/100km (UK gallon) | L/100km (US gallon) |
|---|---|---|
| 15 | 18.83 | 15.68 |
| 20 | 14.12 | 11.76 |
| 25 | 11.30 | 9.41 |
| 30 | 9.42 | 7.84 |
| 35 | 8.07 | 6.72 |
| 40 | 7.06 | 5.88 |
| 45 | 6.28 | 5.23 |
| 50 | 5.65 | 4.70 |
| 55 | 5.14 | 4.28 |
| 60 | 4.71 | 3.92 |
| 65 | 4.35 | 3.62 |
| 70 | 4.04 | 3.36 |
Read the gap between the two columns as the price of guessing the gallon. At 40 MPG the gap stands at 1.18 L/100km, and that gap grows as the MPG figure falls, which is why thirsty cars suffer the worst conversion errors.
L/100km to MPG conversion table
The table below runs the trip in reverse, from 4 to 15 L/100km, for readers holding a European or Pakistani figure who need the MPG number a seller or a review quoted.
| L/100km | MPG (UK gallon) | MPG (US gallon) |
|---|---|---|
| 4 | 70.62 | 58.80 |
| 5 | 56.50 | 47.04 |
| 6 | 47.08 | 39.20 |
| 6.5 | 43.46 | 36.19 |
| 7 | 40.35 | 33.60 |
| 8 | 35.31 | 29.40 |
| 9 | 31.39 | 26.13 |
| 10 | 28.25 | 23.52 |
| 11 | 25.68 | 21.38 |
| 12 | 23.54 | 19.60 |
| 13 | 21.73 | 18.09 |
| 14 | 20.18 | 16.80 |
| 15 | 18.83 | 15.68 |
The same number with two gallons
The chart below draws one candle per MPG figure, and each candle spans the two L/100km answers that the number can produce, US gallon at the low end and UK gallon at the high end.
The bar chart below holds the gallon steady at the UK imperial gallon and shows what common MPG figures cost in fuel per 100 kilometers.
Typical bands help a reader place a result. City cars usually land between 5 and 6.5 L/100km, family sedans between 6 and 8.5, SUVs between 8.5 and 13, and pickups above that. A result far outside the band for its class deserves a second look at the gallon setting before it deserves worry about the car.
Worked examples
Three examples show the exact arithmetic the converter runs, so a reader with a notebook can check the tool line by line.
Example 1, a UK brochure figure. A hatchback brochure quotes 40 MPG with the imperial gallon. The converter divides 282.481 by 40 and returns 7.06 L/100km. The km/L readout shows 14.16 km/L, which matches the figure style on a Japanese auction sheet for the same class of car.
Example 2, a US review figure. An American review quotes 30 MPG with the US gallon. The converter divides 235.215 by 30 and returns 7.84 L/100km. A reader who ran that number through the UK constant would get 9.42 L/100km and would judge the car a full class thirstier than the car is.
Example 3, the reverse trip. A European listing states 6.5 L/100km. With the US gallon the converter returns 36.19 MPG, and with the UK gallon it returns 43.46 MPG. Both answers are correct, and each belongs to a different gallon, which is the whole lesson of this page in one line.
Common mistakes with MPG figures
Trusting the first converter result. Most converters apply the US gallon silently. A reader comparing a UK car against a US review then compares two different units and blames the cars. Check the gallon label before you check the number.
Reading L/100km like MPG. A bigger L/100km figure means a thirstier car. Readers raised on MPG often celebrate 12 L/100km as a strong score, and 12 L/100km equals about 23.5 MPG with the UK gallon, which no family car owner would celebrate.
Mixing test cycles with units. A European WLTP figure and an American EPA figure describe the same car through different laboratory tests, and unit conversion alone cannot reconcile them. Convert the units first, then remember that the test behind each number also differs.
Judging a car on one trip. A dashboard average after a short motorway run flatters almost every car. Fill the tank, record the distance, fill again, and let the pump do the arithmetic over a full tank before you call a figure real.
Why I built this converter
I built this tool at a family kitchen table in Multan, and the problem wore a number plate. A relative was choosing between two imported hatchbacks. One car appeared on a Japanese auction sheet in km/L, and the other appeared on a UK site in MPG. I ran both figures through the converters I found online, and every one of them applied the US gallon without saying so. The UK car came out looking thirstier than it was, and the family nearly rejected the better car on the strength of a setting nobody at the table had chosen.
I slowed the evening down, converted both cars onto one L/100km scale by hand, and the ranking flipped. The car that looked worse on paper used less fuel in real units; the cheaper car on paper was the thirstier one where it counted. That evening settled the design of this page: the gallon selector stays visible, the result states its gallon in words, and the km/L readout sits next to the answer for auction-sheet readers. It also settled a habit I have kept since: I check the gallon behind every MPG figure now, before I check the figure itself.
The guides below grow out of that same comparison habit. Each one takes a single fuel question, works it with real numbers, and shows the method rather than asking for trust.
Guides and worked cases
- The UK car that nearly lost to a wrong gallon
- What 5.0 L/100km costs you on a Multan to Lahore motorway run
- Check a used car's real fuel use before you pay for it
- Why the same car drinks more in Karachi traffic than on the motorway
- Hybrid fuel figures, decoded before you import one
- Your dashboard average is flattering you
- Reading a European listing: WLTP figures without the headache
- Petrol or diesel: the running-cost break-even most buyers skip
- Tyres, load and the AC: what actually moved my average
- Brochure MPG from another era: reading old Pakistani car figures
Questions people ask about this page
Which gallon does my car's brochure use?
A brochure from the United States uses the US gallon, and a brochure from the United Kingdom uses the imperial gallon. Japanese auction sheets usually quote km/L instead, so convert that figure first and compare everything on the L/100km scale.
Why do UK and US figures differ for the same car?
The imperial gallon holds about 20 percent more fuel than the US gallon, according to the NIST conversion values. A car therefore travels more miles on one imperial gallon, and the same car earns a higher MPG number in the UK than in the US.
Is a higher L/100km figure better or worse?
Worse. L/100km measures fuel consumed over a fixed distance, so a higher number means the car burns more fuel. The scale runs opposite to MPG, where a higher number means better economy.
What is a good L/100km figure for a family car?
A combined figure between 6 and 8 L/100km suits most family sedans in everyday mixed driving. Small city cars often sit between 5 and 6.5 L/100km, and large SUVs commonly sit between 9 and 13 L/100km.
How do I convert km/L to L/100km?
Divide 100 by the km/L figure. A car rated at 14 km/L uses 100 divided by 14, which equals 7.14 L/100km. The converter on this page shows the km/L readout next to every result for that reason.
Why does my car never match the brochure figure?
Brochure figures come from laboratory test cycles, and the EPA states that its ratings are test results, not guarantees of real-world results. Traffic, short trips, air conditioning, tire pressure, and load all move a real figure away from the label figure.
Facts, checked against trusted sources
- One US liquid gallon equals 3.785411784 liters exactly, and one UK imperial gallon equals 4.54609 liters, so the UK gallon is about 20 percent larger than the US gallon. Source: National Institute of Standards and Technology (NIST), Guide for the Use of the International System of Units (SP 811)
- The United States Environmental Protection Agency publishes official MPG ratings for new vehicles, including city, highway, and combined values, through fueleconomy.gov. Source: U.S. Environmental Protection Agency and U.S. Department of Energy, fueleconomy.gov
