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Fuel Consumption Converter

Convert fuel consumption between L/100 km, km/L and miles per gallon (US and UK) in one step. Convert liters to gallons and kilometers to miles. Or enter two odometer readings and the liters you filled to get the real consumption of a vehicle with the full-tank method.

  • Runs in your browser
  • Exact conversion factors
  • US and UK gallons kept apart
The unit you have

In the unit selected above. 12 is an example; use the figure from your spec sheet or fuel records.

How this is converted
km/L = 100 ÷ L/100 km mpg (US) = 235.215 ÷ L/100 km mpg (UK) = 282.481 ÷ L/100 km L/100 km = 100 ÷ km/L = 235.215 ÷ mpg (US) = 282.481 ÷ mpg (UK)

The factors come from the exact definitions of the gallon and the mile. See the method below.

Consumption in every unitExact factors

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Report with your inputs, every unit and the full-tank result.

Fuel consumption report

Get the conversion and the full-tank result in one report

  • Your figure in L/100 km, km/L and mpg (US and UK)
  • Volume and distance conversions
  • Distance, liters and consumption from the full-tank method
  • Fuel cost per 100 km and the gap to your target
  • Conversion factors and next steps

What are the units of fuel consumption?

Fuel consumption is stated in two ways. L/100 km gives the liters a vehicle uses to cover 100 km, so a lower figure is better. km/L and miles per gallon (mpg) give the distance covered with one unit of fuel, so a higher figure is better.

Spec sheets, trip computers and fuel reports often use different units. A vehicle imported from the United States may show mpg in US gallons, a British one mpg in UK (imperial) gallons, and a fleet report L/100 km. This fuel consumption converter puts all of them side by side so you compare like with like.

How do you convert L/100 km, km/L and mpg?

All four units are reciprocal. Convert any figure to L/100 km first, then to the unit you need:

km/L = 100 ÷ L/100 km mpg (US) = 235.215 ÷ L/100 km mpg (UK) = 282.481 ÷ L/100 km mpg (UK) = mpg (US) × 1.20095

The constants follow from exact definitions: 1 US gallon = 3.785411784 liters, 1 UK gallon = 4.54609 liters and 1 mile = 1.609344 km (NIST Handbook 44, Appendix C). For example, 235.215 = 100 × 3.785411784 ÷ 1.609344.

How do you calculate fuel consumption with the full-tank method?

  1. Fill the tank to the top and write down the odometer reading.
  2. Drive as usual, ideally 300 km or more.
  3. Fill to the top again, at the same pump if possible, and write down the odometer reading and the liters added.
  4. Divide the liters added by the distance and multiply by 100. The result is L/100 km.

The liters added at the second fill are the fuel used since the first fill. Repeat over several fills and average the results for a figure you can rely on.

Worked example

The default values are examples; replace them with your own.

  • Consumption: 12 L/100 km equals 8.33 km/L, 19.6 mpg (US) and 23.5 mpg (UK).
  • Volume and distance: 200 liters equals 52.83 US gallons or 43.99 UK gallons; 100 km equals 62.14 miles.
  • Full-tank method: odometer 45,200 then 45,850 gives 650 km. With 78 liters added, consumption is 78 ÷ 650 × 100 = 12.0 L/100 km.
  • Cost: at USD 0.48 per liter, the fill cost USD 37.44, or USD 5.76 per 100 km.
  • Target: against a target of 11 L/100 km the vehicle used 9.1% more fuel, about 6.5 liters over this distance.

How do you read the figures?

  • L/100 km adds up directly. Liters = distance × L/100 km ÷ 100, so it is the easiest unit for fleet budgets and for the Fleet Fuel Cost Calculator.
  • mpg and km/L are not linear in fuel. Moving from 10 to 12 mpg (US) saves 3.92 L/100 km. Moving from 30 to 32 mpg (US) saves only 0.49 L/100 km. Compare vehicles in L/100 km before you judge a saving.
  • One full tank is one sample. Load, route, idling and air conditioning change the result. Track it over weeks in the Fleet Fuel Log Template.

Common conversion mistakes

  • Mixing US and UK gallons. A UK gallon is about 20% larger, so the same vehicle shows a higher mpg in UK gallons.
  • Partial fills. If either fill stops before the tank is full, the liters no longer match the distance.
  • Short distances. Below about 100 km, a small difference in where the pump stops changes the result noticeably.
  • Odometer in miles, liters at the pump. Select miles as the odometer unit; the converter turns the distance into kilometers before dividing.

Assumptions and limits

Conversions use exact definitions and are not estimates. The full-tank result is only as accurate as the fills and the odometer: pump shut-off points differ, and an odometer can be off when tire sizes change. Price and target are your inputs; the defaults are examples. To check that the fuel you buy matches the distance driven, compare fills with the Fuel Card Leakage Calculator.

Related Safee solution

Measure consumption for every vehicle without manual calculations

Safee Fuel Tracking reads fuel data from each vehicle, so consumption per trip and per 100 km comes from measured data, not from receipts and odometer notes.

  • Consumption per trip and per 100 km, with the fuel history of each vehicle.
  • Refueling detection and alerts on sudden drops in the fuel level.
  • CANbus and external fuel sensors, with calibration for more reliable readings.
  • Exportable and scheduled reports for finance and operations.
Questions

Questions about fuel consumption conversion

Need help with your fleet's fuel figures? Talk to Safee.

How do I convert L/100 km to km/L?

Divide 100 by the L/100 km figure. 12 L/100 km is 100 ÷ 12 = 8.33 km/L. The same formula works the other way: 100 ÷ km/L gives L/100 km.

How do I convert mpg to L/100 km?

Divide 235.215 by the mpg figure if it uses US gallons, or 282.481 if it uses UK gallons. 25 mpg (US) is 9.41 L/100 km; 25 mpg (UK) is 11.30 L/100 km.

Why are US and UK mpg different?

The gallons differ. A US gallon is 3.785 liters and a UK gallon is 4.546 liters, so the same vehicle shows about 20% more miles per UK gallon. Check which gallon a spec sheet uses before you compare.

How do I calculate fuel consumption from the odometer?

Fill the tank to the top and note the odometer. At the next full fill, note the odometer and the liters added. Divide the liters by the distance and multiply by 100 to get L/100 km.

Why does my result differ from the trip computer?

A trip computer estimates fuel from engine data, and pumps stop at slightly different levels. Average several full-tank results, or use measured fuel data from sensors or CANbus.

Which unit should a fleet use?

Use one unit in all reports. L/100 km is the easiest for budgets because liters = km × L/100 km ÷ 100. If drivers know km/L better, show both.

How many liters are in a gallon?

A US gallon is exactly 3.785411784 liters and a UK (imperial) gallon is exactly 4.54609 liters. One liter is 0.264 US gallons or 0.220 UK gallons.

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