So, I have the problem to convert mpg to lp100km.

I have tried to calculate them by hand, given that 1 mile = 1.60934 km and 1 gallon = 3.78541 litres, and it yields me like: 1 mpg = 235.133 lp100km

However, when I searched for the conversion online, there are different values and it makes me confused whether my answer is right or not.

I have also tried to convert back, what I mean here is lp100km->mpg. But why did I get the same result, i.e. 1 lp100km = 235.133 mpg

Can anyone help me with this?


  • $\begingroup$ $1$ mile per gallon gives something very close to what you got. With the conversion numbers of the post (which I have not checked) I get about $235.215$. Perhaps you rounded during the calculation. $\endgroup$ Sep 13 '14 at 4:47
  • $\begingroup$ The kind of precision we used is meaningless. Fuel consumption figures, in say miles per gallon, are at best rough estimates. $\endgroup$ Sep 13 '14 at 4:56
  • $\begingroup$ Pedantic: 1 mile = 1.609344 km $\endgroup$ Jan 19 '21 at 14:45

Simple unit analysis: \begin{align*} 1 \frac{\text{mile}}{\text{gallon}} \times \frac{1.60934}{1} \frac{\text{km}}{\text{mile}} \times \frac{1}{100} \frac{\text{100 km}}{\text{km}} \times \frac{1}{3.78541}\frac{\text{gallon}}{\text{L}} = 0.00425142 \frac{\text{100 km}}{\text{L}}, \end{align*} and so, 1 mpg is equivalent to $\frac{1}{0.00425142} = 235.215 \frac{\text{L}}{\text{100 km}}$.

However, keep in mind that mpg and L/100 km are inverse units, so 10 mpg would be equivalent to 23.5215 L/100 km.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.