Convert MPG (US) to L/100km miles per US gallon ↔ litres per 100 kilometres Free Online Secure
Type a figure in miles per US gallon and read it in litres per 100 kilometres at once. These two run opposite ways — one counts fuel per distance, the other distance per fuel — so the page divides rather than multiplies.
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Convert from miles per US gallon
Convert to litres per 100 kilometres
Common values — Convert MPG (US) to L/100km (miles per US gallon ↔ litres per 100 kilometres)
| MPG (US) | L/100km |
|---|---|
| 15 | 15.6809722222 |
| 20 | 11.7607291667 |
| 25 | 9.40858333333 |
| 30 | 7.84048611111 |
| 35 | 6.72041666667 |
| 40 | 5.88036458333 |
| 50 | 4.70429166667 |
| 60 | 3.92024305556 |
Where these units come from
Fuel economy is said in two opposite ways. Litres per 100 km asks how much fuel a fixed distance costs; miles per gallon and kilometres per litre ask how far a fixed amount of fuel goes. One is the reciprocal of the other, which is why this page multiplies and divides rather than scaling. Europe settled on litres per 100 km in the 1970s precisely because it is linear in the thing you actually pay for: halve the number and you halve the fuel. The United States kept miles per gallon, and Britain kept it too but with the imperial gallon — a fifth larger — so the same car scores about 20% better in British figures than in American ones without a single part having changed.
Where you meet them
These numbers decide which car gets bought, what a fleet costs to run, how company-car tax is assessed in several countries, and whether a long trip is worth driving rather than flying. They also appear on every new-car window sticker, measured on a standard test cycle rather than on a real road — which is why the figure is best used to compare one car with another, not to predict what your own week will cost.
Questions people ask
Why does the same car get a better mpg figure in Britain than in America?
Because the gallons are different. The imperial gallon is 4.54609 litres and the US gallon 3.785411784 litres, about a fifth smaller. A car that travels 30 miles on a US gallon travels the same distance on less than a British gallon, so its British figure comes out around 36 mpg. Nothing about the car changed; only the size of the container did. Always check which gallon a figure means before comparing two cars across the Atlantic.
Why is litres per 100 km considered the better measure?
Because miles per gallon flatters improvements at the top and hides them at the bottom. Going from 10 to 15 mpg saves twice as much fuel over the same distance as going from 30 to 50 — which is the opposite of what the numbers look like. Litres per 100 km has no such trap: the saving is simply the difference between the two figures. This is why fuel-saving decisions are easier to judge in litres per 100 km, even where mpg is what everyone quotes.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
MPG (US) to L/100 km: why miles per gallon misleads and litres per 100 km does not
Miles per gallon feels natural, because more miles from a gallon sounds better, yet the scale hides the real savings. Going from 10 to 20 mpg saves far more fuel than going from 30 to 50, and nearly everyone gets this wrong when they think in mpg. Researchers named it the MPG illusion, and it is one reason the American window label now also shows gallons per 100 miles. Litres per 100 km avoids the trap, because equal drops in the figure are equal savings. To convert MPG (US) to L/100km, divide 235.2 by the mpg: 15 mpg is 15.7 L/100 km, 25 mpg is 9.41 L/100 km, 40 mpg is 5.88 L/100 km and 60 mpg is 3.92 L/100 km. The gallon is the US gallon. The calculator above divides as you type, and the sections that follow show what the numbers mean for buying decisions, fleets and fuel bills.
Below come the rule with examples, short notes on each unit, a side-by-side look and a long series of ownership and fleet cases, ending with the slips people make most. Everything is computed locally in the page. Official fuel economy is a laboratory figure and your own driving will differ.
How to convert MPG (US) to L/100km: divide 235.2 by the mpg
The rule
A US gallon holds 3.785412 litres and a mile is 1.609344 km, which makes 1 mpg equal to 235.215 L/100 km. The consumption in litres per 100 km is therefore 235.215 divided by the mpg. For a “convert MPG (US) to L/100km” calculation, take 235.215 / 18 = 13.1 L/100 km, 235.215 / 32 = 7.35 L/100 km and 235.215 / 48 = 4.90 L/100 km. The same division turns L/100 km into mpg.
The intermediate unit
Gallons per 100 miles is 100 divided by mpg, and it turns into litres per 100 km by multiplying by 2.352. So 4 gal/100 mi is 9.41 L/100 km. It is the unit on the newer EPA labels and it has the same property as L/100 km: equal differences are equal savings.
Worked examples
A pickup at 17 mpg uses 13.8 L/100 km, a crossover at 29 mpg uses 8.11, a sedan at 37 mpg uses 6.36 and a hybrid at 54 mpg uses 4.36 L/100 km.
A quick sanity test
Multiply the two figures and expect about 235: a car at 25 mpg and 9.41 L/100 km gives 235.3. A product far from that means the “convert MPG (US) to L/100km” calculation went wrong.
Miles per US gallon
The American habit
Miles per gallon expresses how far a vehicle goes on a fuel quantity, so a bigger number looks better. It has been the American standard since the 1970s, when the first federal fuel-economy rules appeared.
Where it appears
EPA window labels, American reviews, regulations and sales brochures.
Litres per 100 kilometres
The measure that adds up
Litres per 100 km gives the fuel needed for a fixed distance. Two cars driven 100 km each use the sum of their figures, and a saving of 1 L/100 km is a saving of 1 litre in every 100 km whatever the starting point.
Where it appears
Labels in Europe, Canada and Australia, and fleet reports in metric countries.
MPG set beside L/100 km
The two scales point in opposite directions and are not proportional: 10 mpg becomes 23.5 L/100 km, 20 mpg becomes 11.8, 40 mpg becomes 5.88 and 80 mpg becomes 2.94. Every doubling of mpg halves the litres, and the product of each pair stays at 235.2.
Nothing is lost on the way. The mistake seen most often is taking the US gallon for the British one, which puts the result 20 per cent off.
Where the conversion shows up
Which upgrade saves more?
Replacing a truck that does 15 mpg with one that does 19 saves 3.3 L/100 km, from 15.7 to 12.4. Replacing a car that does 34 mpg with one that does 44 saves only 1.6 L/100 km, from 6.9 to 5.4. The smaller mpg gain is worth twice as much. A “convert MPG (US) to L/100km” calculation before and after shows it at once.
Reading the American label
The EPA label shows combined, city and highway mpg, annual fuel cost, a five-year saving against the average new vehicle, and gallons per 100 miles. A car rated 28 combined uses 3.57 gal per 100 miles, 8.40 L/100 km. The combined figure weights city driving 55 per cent and highway 45 per cent.
Annual fuel use
At 12,000 miles, 19,312 km, a year a car at 25 mpg uses 480 gallons, 1,817 litres, a car at 35 mpg uses 343 gallons, 1,298 litres, and a car at 50 mpg uses 240 gallons, 908 litres. The difference between 25 and 35 mpg is 137 gallons, 519 litres a year.
The MPG illusion in numbers
Moving from 10 to 20 mpg takes consumption from 23.5 to 11.8 L/100 km, a saving of 11.8 L. Moving from 20 to 30 saves 3.9 L, and from 30 to 50 saves 3.1 L. A buyer thinking in mpg sees steps of 10, 10 and 20 and expects the last to be the biggest, when it is the smallest.
Electric vehicles
The EPA's MPGe uses 33.7 kWh as one gallon. An electric car rated 100 MPGe uses 33.7 kWh per 100 miles, 20.9 kWh per 100 km. Converted to a petrol equivalent, that is 2.35 L/100 km. The figure compares energy use, but cost depends on the price of electricity, which is why the label also gives dollars.
Carbon dioxide per kilometre
Petrol gives 2.31 kg of carbon dioxide per litre. At 30 mpg, 7.84 L/100 km, a car emits 181 g/km, at 40 mpg, 5.88 L/100 km, 136 g/km, and at 50 mpg, 4.70 L/100 km, 109 g/km. The relationship between mpg and emissions is not linear, so converting to litres first makes the arithmetic clear.
Tanks and range
A car with a 15 gallon tank, 57 litres, at 30 mpg, 7.84 L/100 km, goes 450 miles, 724 km. At 45 mpg, 5.23 L/100 km, the same tank gives 675 miles, 1,086 km. Range is tank size divided by L/100 km, times 100, and a large tank can mask poor economy.
A worked example
You are choosing between a crossover rated 24 mpg and a hybrid rated 41. The crossover is 9.80 L/100 km and the hybrid 5.74. At 15,000 km a year the hybrid saves 609 litres, 161 gallons, or 563 dollars at 3.50 dollars a gallon. A “convert MPG (US) to L/100km” calculation on each shows that the hybrid's saving comes from 4.06 L every 100 km.
The mental shortcut
To convert MPG (US) to L/100km without a calculator, divide 240 by the mpg and then knock off 2 per cent. At 30 mpg that gives 8, less 0.16, or 7.84, which is exact. Using 250 instead of 240 is quicker but runs about 6 per cent high.
Spreadsheet formulas
Put the mpg in column A, then =235.215/A2 in column B returns L/100 km, and the same formula pointed the other way returns mpg. =100/A2 gives gallons per 100 miles, and =A2*0.425144 gives km/L for a cross-check.
Rounding on labels
The US label prints mpg as a whole number, so one extra mpg at 28 changes L/100 km by about 0.3. Two decimals are plenty. Laboratory repeatability is 3 to 5 per cent, and no third digit can carry meaning.
Landmarks to memorise
Remember: 10 mpg = 23.5 L/100 km, 15 = 15.7, 20 = 11.8, 25 = 9.4, 30 = 7.8, 40 = 5.9, 50 = 4.7 and 60 = 3.9. With them a mental convert MPG (US) to L/100km takes a moment.
Reference ladder
12 mpg: 19.6 L/100 km. 19 mpg: 12.4. 27 mpg: 8.71. 36 mpg: 6.53. 44 mpg: 5.35. 56 mpg: 4.20. With a list of this kind any result can be checked quickly.
Checking by reversing
Test a “convert MPG (US) to L/100km” calculation answer by dividing 235.2 by it: 6.53 L/100 km gives 36.0 mpg, so the 36 you started from came through intact. A second sign of a good result is that the product is close to 235.
Gallons per 100 miles on the label
Since 2013 the US label has shown gallons per 100 miles. A car rated 25 mpg is 4.0 gal per 100 miles, which is 9.41 L/100 km, and a car rated 40 is 2.5, which is 5.88. The difference of 1.5 gallons per 100 miles is 3.53 L/100 km. A “convert MPG (US) to L/100km” calculation then gives the same difference in a metric country.
Link to km/L and imperial mpg
In 30 US mpg there are 12.75 km/L, 7.84 L/100 km and 36.0 imperial mpg. The 4.546 litre imperial gallon makes the same consumption look 20 per cent better. The units differ and the consumption does not, so a “convert MPG (US) to L/100km” calculation only relabels it.
Two routes to one answer
Go straight with 235.215 divided by the mpg, or travel via gallons per 100 miles and multiply by 2.352. A further path uses km/L: mpg × 0.4251, then 100 divided by that. If the answers drift apart, a digit slipped somewhere.
Air conditioning
Air conditioning can cut fuel economy by 5 to 25 per cent in hot weather, according to US government tests. A car rated 30 mpg, 7.84 L/100 km, may return 22.5 mpg, 10.5 L/100 km, in a heatwave with the compressor running flat out. A “convert MPG (US) to L/100km” calculation on both figures shows the extra 2.6 litres per 100 km that cooling costs.
Driving style
Aggressive driving, with hard acceleration and braking, can lower highway fuel economy by 15 to 30 per cent and town economy by up to 40 per cent. A car that does 30 mpg, 7.84 L/100 km, calmly might do 21 to 25.5 mpg, 9.2 to 11.2 L/100 km, when driven hard. The saving from smooth driving is free.
Engine size within a model line
Engine size matters even within one model line. A 2.0 litre version rated 33 mpg, 7.13 L/100 km, uses 2.7 litres per 100 km less than a 3.5 litre version rated 24 mpg, 9.80 L/100 km. Over 15,000 km a year that is 400 litres, 106 gallons. The conversion shows the cost of the larger engine in the unit the pump uses.
Fleet decisions
A fleet of 10 trucks driving 20,000 miles each a year uses 13,333 gallons at 15 mpg and 10,000 at 20 mpg. Replacing the trucks saves 3,333 gallons, 12,617 litres, about 11,700 dollars at 3.50 dollars a gallon. In metric terms consumption goes from 15.7 to 11.8 L/100 km. Fleet managers compare cost per mile, not mpg.
Heavy trucks
A heavy tractor-trailer averages 6 to 7 mpg, 33.6 to 39.2 L/100 km. A truck at 8 mpg uses 29.4 L/100 km and saves 4.2 to 9.8 L per 100 km against one at 6 or 7. Over 100,000 miles, 160,934 km, that is 6,800 to 15,800 litres. At this end of the scale small mpg gains are very valuable.
Buses and vocational vehicles
A city bus gets 3 to 4 mpg, 58.8 to 78.4 L/100 km, and a school bus 7 to 10 mpg, 23.5 to 33.6 L/100 km. A refuse truck is near 3 mpg, 78 L/100 km. These vehicles stop and start constantly, so fuel per mile is high even with efficient engines, which is why hybrid and electric drives pay off quickest there.
Ethanol blends
A litre of E85 holds about 27 per cent less energy than a litre of petrol, so a flex-fuel car that does 24 mpg on petrol, 9.8 L/100 km, does about 17.5 on E85, 13.4 L/100 km. Ordinary E10 petrol costs about 3 per cent in mpg. Compare fuels by cost per mile, which needs the price per gallon and the mpg.
Diesel against petrol
Diesel holds about 12 per cent more energy per litre than petrol, so a diesel at 30 mpg, 7.84 L/100 km, uses about the same energy as a petrol car at 27 mpg, 8.7 L/100 km. Mpg alone therefore flatters the diesel. For a fair comparison, convert the mpg of each to energy per distance.
Weather and speed
The Department of Energy puts the cost of speed at about 7 per cent for every 5 mph above 50, and cold short trips at up to 15 per cent. A car rated 32 mpg, 7.35 L/100 km, might return 27 mpg, 8.7 L/100 km, in winter town driving, and 29 mpg, 8.1 L/100 km, at 80 mph on a mild day.
Loads and drag
Every extra 100 lb, 45 kg, reduces mpg by about 1 per cent in a small car. A load of 300 kg turns 35 mpg, 6.72 L/100 km, into 32.7 mpg, 7.2 L/100 km. A roof box at highway speed can cost 5 to 15 per cent, so the effect of carrying equipment is larger than most owners expect.
More values for convert MPG (US) to L/100km
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 3 MPG (US) = 78.4049 L/100km
- 7 MPG (US) = 33.6021 L/100km
- 9 MPG (US) = 26.135 L/100km
- 12 MPG (US) = 19.6012 L/100km
- 15 MPG (US) = 15.681 L/100km
- 20 MPG (US) = 11.7607 L/100km
- 35 MPG (US) = 6.72042 L/100km
- 40 MPG (US) = 5.88036 L/100km
Common slips with a “convert MPG (US) to L/100km” calculation
Multiplying by a constant
The conversion is a division of a constant. Multiplying 30 by 235 gives 7,050, which is not a consumption of any car. Divide 235.2 by the mpg.
British and American gallons
40 US mpg is 5.88 L/100 km, while 40 imperial mpg is 7.06. Confirm the gallon before you convert, especially for cars discussed in British magazines.
Averaging mpg
The average of two mpg figures is not the average consumption. Convert to litres per 100 km, average those, and convert back if you wish.
Short answers
How do I convert MPG (US) to L/100km?
Take 235.2 and divide it by the mpg.
What is 30 mpg in L/100 km?
It is 7.84 L/100 km.
What is 20 mpg in L/100 km?
It is 11.8 L/100 km.
What is 8 L/100 km in mpg?
It is 29.4 mpg.
Is my number sent anywhere?
No, everything is computed in the browser.
More pages and a wrap-up
Other fuel-economy conversions are listed in Convert MPG (US) to km/L, Convert MPG (US) to MPG (UK), Convert MPG (UK) to L/100km, Convert km/L to L/100km, Convert L/100km to km/L, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. Going the other way is covered by Convert L/100km to MPG (US).
To sum up, a “convert MPG (US) to L/100km” calculation needs one division of 235.2 by the mpg and a unit beside the answer. The figure is worked out on your own device, without registration or upload.