12 replies to this topic

[NetOne]

Does anyone know the formula to convert between mpg & L/100km ? Do you guys use gallon as 4.54609L, 4.40488377086L or 3.785411784 litres in calculation ?

Just wondering why it use miles per gallon for fuel consumption while the petrol pumping at the station measure in litre. Isn't it a bit hassle that one has to convert it to gallon in order to calculate for fuel consumption after each refill (If we want to know)

[Rob]

loads of conversion calculators on the net

[IanB]

It's 4.546 for imperial gallons to litres.

IanB

[RoadRash]

We calculate 1gal = 3,8L

[1972pixie]

Does anyone know the formula to convert between mpg & L/100km ? Do you guys use gallon as 4.54609L, 4.40488377086L or 3.785411784 litres in calculation ?

Just wondering why it use miles per gallon for fuel consumption while the petrol pumping at the station measure in litre. Isn't it a bit hassle that one has to convert it to gallon in order to calculate for fuel consumption after each refill (If we want to know)

It's no problem really simple calculation litres divided by 4.544 = gallons then mileage divided by gallons = MPG

It's what you get used

[Noel]

UK gallon is equal to 4.546 litres

American gallon is equal to 3.7854 litres...

[MacRS200]

Does anyone know the formula to convert between mpg & L/100km ? Do you guys use gallon as 4.54609L, 4.40488377086L or 3.785411784 litres in calculation ?

MPG x 0.314 = L/100Km
L/100Km x 3.191 = MPG

Just wondering why it use miles per gallon for fuel consumption while the petrol pumping at the station measure in litre. Isn't it a bit hassle that one has to convert it to gallon in order to calculate for fuel consumption after each refill (If we want to know)

We use miles for distance so we would have to convert miles to Kilometres to work out L/100Km anyway. Also L/100Km mean nothing to me

[eXOBeX]

That ain't right, surely?

That would mean that if a car does 10mpg it would use 3.14 litres, but if it does 100mpg it would use 31.4 litres - ten times more efficient, yet ten times more fuel!

Looking at figures on the net, if you multiply a car's mpg rating by its l/100km rating you get 282 or thereabouts, basically the "magic number" is 100 x number of gallons in a litre divided by number of kilometres in a mile.

Therefore to get one, divide the "magic number" by the other. Works both ways.

For Imperial Gallons, the magic number is 282.5357.
For US Gallons, the magic number is 235.2393.

e.g. a car which does 30mpg does 282.5357/30 = 9.4179l/100km

[Dilbert D]

1 mpg = 282.481 Litre/100km = 2.82481 Litre/km (For UK gallon)
1 mpg = 235.215 Litre/100km = 2.35215 Litre/km (For US gallon)

[smw]

http://www.geocities.com/mpgcalc/

[crazylex]

I use this to work out how much fuel my car uses.

The answer is always the same : Loads


Even when exponentially smoothed

[NetOne]

Thanks guys for clarifying the unit value for UK & US gallon. No wonder some people in this forum quote way far more for their mpg (fuel consumption) than the others, probably one is referring to UK gallon while the other is referring to US gallong.

Here's what I've came up with the calculation for UK gallon
Miles Per Gallon to Litres Per 100 Kilometer
1 mile = 1.609344 km
1 gallon = 4.54609 litres

If 1 gallon gives 37.2 miles then 4.54609 litres gives 59.8675968 km

Hence litres per 100 km
= 100 / (mpg * 1.609344 km / 4.54609 litres)
= 100 * (4.54609 litres / mpg * 1.609344 km)
= 282.48093633182215859381213711922 / mpg
ie. L/100km = 282.481/mpg
and mpg = 282.481 / L/100km (Thanks eXOBeX for the correction)
Where mpg and L/100km is a number quoted for fuel consumption.

Similarly for US gallon except that 1 gallon equals 3.785411784 litres not 4.54609 litres

[eXOBeX]

That last formula should read
mpg = 282.481 / L/100km