Fuel Economy Converter: L/100 km, km per Litre and Miles per Gallon with Trip Cost and CO2

Convert fuel consumption between units and cost a trip.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

Choose the unit your figure is in and enter it.

Enter the trip distance, the fuel price and the fuel type.

The calculator gives the figure in every unit, the fuel used on the trip, its cost and the carbon dioxide.

Formulas used

  • \mathrm{mpg_{US}} = \frac{235.215}{L/100\,\mathrm{km}}
  • \mathrm{mpg_{UK}} = \frac{282.481}{L/100\,\mathrm{km}}
  • V = \frac{(L/100\,\mathrm{km})\times d}{100}

Worked example

With the default numbers in the calculator above:

  1. Litres per 100 km: 8
  2. Kilometres per litre: 12.5 km/L
  3. Miles per US gallon: 29.402 mpg (US)
  4. Miles per UK (imperial) gallon: 35.31 mpg (UK)
  5. Fuel used on the trip: 40 litres
  6. Cost of the fuel for the trip: 80 dollars (16 dollars per 100 km)
  7. Carbon dioxide emitted by burning that fuel: 92.4 kg (184.8 g per km)

Change the numbers in the calculator to see the full working, every step, for your own case.

A second worked example

A different case, with these numbers: The figure you have is in Miles per US gallon; The fuel economy figure 30.

  1. Litres per 100 km: 7.8405
  2. Kilometres per litre: 12.754 km/L
  3. Miles per US gallon: 30 mpg (US)
  4. Miles per UK (imperial) gallon: 36.028 mpg (UK)
  5. Fuel used on the trip: 39.202 litres
  6. Cost of the fuel for the trip: 78.405 dollars (15.68 dollars per 100 km)
  7. Carbon dioxide emitted by burning that fuel: 90.558 kg (181.1 g per km)

Common questions

How do I convert L/100 km to mpg?

Divide 235.215 by the L/100 km figure for US mpg, or 282.481 for UK mpg. 8 L/100 km is 29.4 US mpg.

Why is a UK gallon different from a US gallon?

The UK (imperial) gallon is 4.546 litres and the US gallon is 3.785 litres, so the same car has a higher mpg in UK units.

How much CO2 does a litre of petrol make?

About 2.31 kg of carbon dioxide from burning it.

Related calculators

Got a question about this? Ask an engineering question and get a plain-language answer with references.

Further reading: Standard unit conversion factors. Emission factors are typical round values for combustion only.

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