Sunday, 17 October 2010

Converting miles per gallon (mpg) to litres per hundred kilometres (l/100 km)

There are a couple of online converters e.g. here, but actually it's simpler than that. The magic number is 282.5 (or 235.2 if you're in the USA).*

So if you know mpg and want to know l/100 km, you divided 281 by mpg, and vice versa. For example 28 mpg = 10 l/100 km.

* Remember that the two fractions are 'other way up', i.e. high mpg = good fuel economy, but low l/100 km = good fuel economy:

One imperial gallon = 4.5461 litres
One mile = 1.609344 kilometres
4.5461 divided by 1.609344 = 2.825 and times by 100 = 282.5

One US gallon = 3.7854 liters
One liter = 1 litre
One mile = 1.609344 kilometres
3.7854 divided by 1.609344 = 235.2

7 comments:

James Higham said...

I became used to the litres one but never liked it. Mpg was easier. But in the other, we generally looked for 10.0 or lower.

Lola said...

It's Sunday! Go for walk. You really need to get out more.

Tim Almond said...

you can actually use Google as a calculator and converter. Just type in something like 52 mpg in l/km and it gives you the result.

Mark Wadsworth said...

JH, you can become used to either but mpg is quicker to calculate.

L, I'm doing this in between cooking Sunday lunch.

JT, sure, but now you can do it in your head!

DBC Reed said...

With Lola on this one.Why would you ever need to make this conversion?

Mark Wadsworth said...

DBC, why? Because some car advertisements talk in terms of l/100 km. So if it says "7 l/100 km" you can quickly convert this to 40 mpg and think "that's pretty good", for example.

Steven_L said...

The fuel computer on my old Mazda 6 did it in litres/100 miles.

I just used to work on 9 = 50mpg and 13.5 = 33mpg.

I traded down to an old banger to rid my life of depreciation, I haven't a clue how much fuel it uses.