Convert L/100km to MPG (UK) litres per 100 kilometres ↔ miles per imperial gallon Free Online Secure
Type a figure in litres per 100 kilometres and read it in miles per imperial gallon 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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Common values — Convert L/100km to MPG (UK) (litres per 100 kilometres ↔ miles per imperial gallon)
| L/100km | MPG (UK) |
|---|---|
| 3 | 94.1603121106 |
| 4 | 70.620234083 |
| 5 | 56.4961872664 |
| 6 | 47.0801560553 |
| 7 | 40.354419476 |
| 8 | 35.3101170415 |
| 10 | 28.2480936332 |
| 12 | 23.5400780277 |
| 15 | 18.8320624221 |
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.
L/100 km to MPG (UK): litres at the pump, miles per gallon in the head
British motorists buy fuel by the litre but judge a car by miles per imperial gallon, a mix of metric and imperial that confuses visitors and delights nobody. A European label of 5 litres per 100 km becomes 56.5 mpg in a British advert, while the same car in America would be 47.0 mpg because the US gallon is smaller. The imperial gallon holds 4.546 litres, and the figures are reciprocal, so no single multiplier links litres per 100 km and mpg. To convert L/100km to MPG (UK), divide 282.5 by the consumption: 4 L/100 km is 70.6 mpg, 6 L/100 km is 47.1 mpg, 8 L/100 km is 35.3 mpg and 10 L/100 km is 28.2 mpg. The calculator above divides as you type, and the sections below show what the numbers mean on a British road.
The page gives the rule with worked examples, a profile of each unit, a comparison and a long run of British driving and ownership cases, followed by the usual slips. The calculation runs in your browser and nothing you type is sent anywhere. Real consumption depends on speed, weather and traffic, and the official figure is a laboratory result.
How to convert L/100km to MPG (UK): divide 282.5 by the consumption
The rule
An imperial gallon is 4.54609 litres and a mile is 1.609344 km. Miles per gallon is distance per fuel and L/100 km is fuel per distance, so each is the other's reciprocal. To convert L/100km to MPG (UK), divide 282.481 by the L/100 km: 282.481 / 5 = 56.5 mpg, 282.481 / 7 = 40.4 mpg and 282.481 / 12 = 23.5 mpg. The same division turns UK mpg into L/100 km.
Why it is not a proportion
When consumption halves, mpg doubles: 12 L/100 km is 23.5 mpg, 6 is 47.1 and 3 is 94.2. A simple factor cannot show this, so each figure has to be calculated, and published tables of paired values are only samples of a curve.
Worked examples
A supermini at 5.2 L/100 km makes 54.3 mpg. A diesel estate at 4.6 L/100 km makes 61.4 mpg. A family SUV at 7.8 L/100 km makes 36.2 mpg, and a large four-wheel drive at 11.5 L/100 km makes 24.6 mpg.
A quick sanity test
The product of the two figures should be near 282.5. A car at 8 L/100 km and 35.3 mpg gives 282.4. If a “convert L/100km to MPG (UK)” calculation gave a product far from that, an error crept in, or the US constant was used by mistake.
Litres per 100 kilometres
The measure on the pump and the label
Fuel per distance is what the pump sells and what a European label shows. A smaller number is better, and multiplying by the price per litre gives the cost of every 100 km.
Where it appears
European type approvals, car data sheets and fuel-cost calculators.
Miles per gallon (UK)
The British habit
British drivers talk of miles per imperial gallon, a larger number being better. The UK legislated for fuel to be sold in litres, yet mpg survived on the dashboard, in adverts and in conversation.
Where it appears
British reviews, used-car adverts, dealers and everyday talk about cars.
L/100 km set beside MPG (UK)
The two scales run in opposite directions: 5 L/100 km is 56.5 mpg, 10 is 28.2 and 20 is 14.1. Halve the litres and the mpg doubles, and the product stays at 282.5.
The conversion is exact. The commonest trap is the US gallon, which is 17 per cent smaller than the imperial and gives a result 17 per cent lower.
Where the conversion shows up
Reading a British advert
A used-car advert says "52 mpg". That is 5.43 L/100 km. Read as US mpg it would be 4.52 L/100 km, a gap of 20 per cent in the wrong direction. A European buyer, or a British one who wants the metric number, should divide 282.5 by the mpg. A “convert L/100km to MPG (UK)” calculation the other way round gives the same figure.
Cost per mile
At 1.50 pounds a litre an imperial gallon costs 6.82 pounds. A car doing 40 mpg then costs 17 pence a mile, 10.6 pence per kilometre, and one doing 60 mpg 11.4 pence a mile. Motoring organisations quote costs in pence per mile and fuel in pence per litre, which is why people reach for a calculator.
Speed limits
The motorway limit is 70 mph, 113 km/h, and a single carriageway limit is 60 mph, 97 km/h. A car using 6.3 L/100 km, 45 mpg, at 70 mph might use 7.4, 38 mpg, at 80 mph, nearly a fifth more fuel for a 14 per cent rise in speed. That is the price of speed in either unit.
The WLTP and what it means in mpg
Since 2017 new cars are tested on the WLTP cycle, which gives higher consumption than the old NEDC. A hatchback labelled 5.6 L/100 km, 50.4 mpg, is closer to real use than one labelled 4.4, 64.2 mpg, would have been under NEDC. Real road tests still average 10 to 20 per cent above the label.
Towing and loading
Towing a caravan can take an SUV from 33 mpg, 8.6 L/100 km, to 22 mpg, 12.8 L/100 km, a rise of nearly 50 per cent. A full load of passengers and luggage raises consumption by 5 to 15 per cent. The official figure is measured with a driver and nothing else on board.
E10 petrol
British standard petrol has contained up to 10 per cent ethanol, E10, since 2021. Ethanol holds less energy, so economy falls by 1 to 2 per cent: a car at 50 mpg, 5.65 L/100 km, becomes about 49.3 mpg, 5.73 L/100 km. The difference is small compared with the effect of speed or tyre pressure.
Tyre pressure
Under-inflated tyres raise fuel use. A car whose tyres are 6 psi, 0.4 bar, below the recommendation uses 1 to 2 per cent more fuel, so 45 mpg, 6.28 L/100 km, becomes 44.3 mpg, 6.37 L/100 km. The sticker on the door pillar gives the pressure in both psi and bar.
City against motorway
Stop-start traffic is hard on petrol cars. A car that returns 48 mpg, 5.9 L/100 km, on the motorway may do 34 mpg, 8.3 L/100 km, in town and 27 mpg, 10.5 L/100 km, in a London queue. Hybrids do better in town than on the motorway, the reverse of conventional cars, because they recover energy under braking.
A year of motoring
At 10,000 miles, 16,093 km, a year a car at 44 mpg, 6.42 L/100 km, uses 227 gallons, 1,033 litres, which costs 1,550 pounds at 1.50 pounds a litre. A car at 34 mpg, 8.31 L/100 km, uses 294 gallons, 1,337 litres, and costs 2,006 pounds, a difference of 456 pounds. A “convert L/100km to MPG (UK)” calculation gives the litres behind each bill.
Classic British cars
A classic Mini returns 38 to 48 mpg, 5.9 to 7.4 L/100 km, a diesel Land Rover Defender 20 to 25 mpg, 11.3 to 14.1 L/100 km, and a six-cylinder saloon of the 1980s 17 to 21 mpg, 13.5 to 16.6 L/100 km. Old carburettors and tall gearing are the cause, and the low annual mileage of a classic softens the cost.
A worked example
You compare a British hatchback at 62 mpg with a European one at 4.8 L/100 km. The British one is 4.56 L/100 km and the European one 58.9 mpg. At 15,000 km a year the first uses 683 litres and the second 720 litres, 37 litres more, or 8 gallons. The comparison is only fair if both figures come from the same test.
The mental shortcut
To convert L/100km to MPG (UK) in your head, divide 280 by the consumption and add 1 per cent. For 8 L/100 km: 280 / 8 = 35, plus 0.35 gives 35.35, against the exact 35.31. Dividing 300 by the consumption is simpler but about 6 per cent high.
Spreadsheet formulas
With the L/100 km in column A, put =282.481/A2 in column B for UK mpg. The same formula converts mpg back to L/100 km. As cross-checks, =235.215/A2 gives US mpg and =100/A2 gives km/L.
Rounding on adverts
British adverts print mpg as whole numbers, so 52 mpg is 5.4 L/100 km and not 5.432. Real consumption differs from the label by 10 to 20 per cent, and an extra decimal would suggest accuracy that nobody has.
Small petrol engines
A 1.0 litre three-cylinder turbo advertised at 55 to 60 mpg, 4.7 to 5.1 L/100 km, often returns 42 to 50 mpg, 5.6 to 6.7 L/100 km, on the road. A small turbo is efficient at light load and thirsty when worked hard, so how it is driven matters more than the label.
Landmarks to memorise
4 L/100 km is 70.6 mpg. 5 is 56.5. 6 is 47.1. 7 is 40.4. 8 is 35.3. 10 is 28.2. 12 is 23.5. 15 is 18.8. With these landmarks nearly every mental convert L/100km to MPG (UK) is possible.
Reference ladder
3.8 L/100 km: 74.3 mpg. 5.2: 54.3. 6.8: 41.5. 8.5: 33.2. 10.5: 26.9. 13: 21.7. A table like this lets you test a calculator output at a glance.
Checking by reversing
To check a “convert L/100km to MPG (UK)” calculation result, divide 282.5 by the answer. If 8.5 L/100 km gave 33.2 mpg, then 282.5 / 33.2 = 8.51. A second test is the product, which should be about 282.5.
Link to US mpg and km/L
A consumption of 7 L/100 km is 40.4 UK mpg, 33.6 US mpg and 14.3 km/L. The ratio between the two mpg figures is 1.2009, the ratio of the gallons. These express the same consumption, and a “convert L/100km to MPG (UK)” calculation just swaps the label.
Two routes to one answer
You can divide 282.481 by the L/100 km directly, or go through US mpg: 235.215 divided by the L/100 km, multiplied by 1.2009. A third route uses km/L, 100 divided by the consumption, then multiplied by 2.8248. If the routes disagree, a digit was copied wrongly.
Mild hybrids
A mild-hybrid system uses a small battery and a starter-generator to help the engine and to switch it off while coasting. It typically saves 5 to 10 per cent, taking a car from 47 mpg, 6.0 L/100 km, to 50 to 52 mpg, 5.4 to 5.6 L/100 km. The label figure comes from the laboratory cycle, where such savings are easy to show, and on the road they are smaller.
Diesel
A 2.0 litre diesel estate does 55 to 65 mpg, 4.3 to 5.1 L/100 km, and a large diesel SUV 35 to 42 mpg, 6.7 to 8.1 L/100 km. Diesel contains about 12 per cent more energy per litre than petrol, so mpg alone flatters it. A “convert L/100km to MPG (UK)” calculation on both fuels makes the difference clearer in litres.
Plug-in hybrids and their giant mpg
A plug-in hybrid may be labelled 200 mpg, 1.4 L/100 km, or even more, because the test counts the energy from the battery as free. Once the battery is flat the same car gives 40 to 50 mpg, 5.6 to 7.1 L/100 km. Whether the label is any use depends on how often the owner plugs in.
Electric cars
Electric cars in Britain are rated in miles per kWh. 3.5 miles per kWh is 17.8 kWh per 100 km and 4 miles per kWh is 15.5 kWh. A petrol equivalent of 17.8 kWh per 100 km is 2.0 L/100 km, or about 140 mpg. The cost per mile depends on the tariff and where the car is charged.
Vehicle tax and emissions
Carbon dioxide is the basis of British vehicle taxes. A litre of petrol gives 2.31 kg and a litre of diesel 2.68 kg. A car at 5.65 L/100 km, 50 mpg, on petrol emits 130 g/km, and a diesel at 4.9 L/100 km, 57.6 mpg, emits 131 g/km. The relation between mpg and tax band therefore depends on the fuel.
Tank size and range
A tank of 11 imperial gallons, 50 litres, at 50 mpg, 5.65 L/100 km, gives 550 miles, 885 km. At 35 mpg, 8.07 L/100 km, it gives 385 miles, 620 km. Range is tank size multiplied by mpg, or 100 times tank litres divided by L/100 km, and it falls quickly as consumption rises.
Heavy vehicles
An articulated lorry achieves 8 to 9 mpg, 31.4 to 35.3 L/100 km, and a city bus 5 to 7 mpg, 40.4 to 56.5 L/100 km. Coaches on long journeys do 9 to 11 mpg, 25.7 to 31.4 L/100 km. Haulage firms track litres per 100 km, while the driver sees mpg on the dashboard.
Motorcycles
A 600 cc motorcycle manages 50 to 60 mpg, 4.7 to 5.6 L/100 km, and a 125 cc scooter 100 to 120 mpg, 2.4 to 2.8 L/100 km. British reviewers always quote mpg for bikes, since commuting by motorcycle is sold as a cheap alternative to a car.
More values for convert L/100km to MPG (UK)
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 L/100km = 94.1603 MPG (UK)
- 7 L/100km = 40.3544 MPG (UK)
- 9 L/100km = 31.3868 MPG (UK)
- 12 L/100km = 23.5401 MPG (UK)
- 15 L/100km = 18.8321 MPG (UK)
- 20 L/100km = 14.124 MPG (UK)
- 35 L/100km = 8.07088 MPG (UK)
- 40 L/100km = 7.06202 MPG (UK)
Common slips with a “convert L/100km to MPG (UK)” calculation
The wrong constant
For British figures use 282.5, not the American 235.2. With the wrong constant the result is 17 per cent too low, and the error is easy to miss.
Multiplying instead of dividing
The conversion is a division of a constant. Multiplying 8 by 282 gives 2,256, which is not the consumption of any car.
Averaging mpg
The mean of two mpg figures is not the mean consumption of the two cars. Average the litres per 100 km first, then convert.
Short answers
How do I convert L/100km to MPG (UK)?
Divide 282.5 by the L/100 km.
How many UK mpg is 8 L/100 km?
35.3 mpg.
How many UK mpg is 5 L/100 km?
56.5 mpg.
How many L/100 km is 40 UK mpg?
7.06 L/100 km.
Does my number leave my device?
No, the calculation runs in your browser.
More pages and a wrap-up
For other fuel-economy conversions see Convert L/100km to MPG (US), Convert L/100km to km/L, Convert km/L to MPG (UK), Convert MPG (US) to MPG (UK), Convert MPG (UK) to MPG (US), Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. For the opposite direction see Convert MPG (UK) to L/100km.
In short, a “convert L/100km to MPG (UK)” calculation means one division of 282.5 by the consumption and a unit written next to the result. Your figure is calculated locally, with no account and no upload.