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CALCPARK

Fuel Cost Calculator

Calculate the fuel and cost of a trip from distance, consumption (L/100 km, km/L or mpg) and fuel price, with round trip and cost per passenger.

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How to use it

  1. Enter the distance in km or miles and tick “round trip” if you are coming back the same way.
  2. Enter your car’s consumption in whichever unit you know – L/100 km, km/L, US or UK mpg – and the fuel price per litre or gallon.
  3. Set the number of passengers sharing the cost and, if you like, a currency label.
  4. Read the fuel needed, the total cost, the cost per km or mile and the cost per person; the second panel shows your consumption in all four units.
  5. Copy the summary or the link to send the split to your passengers.

Example

A 300-mile trip in a car doing 30 mpg (US) with petrol at 3.50 per US gallon: 300 ÷ 30 = 10 gallons (37.85 L), cost 35.00, 0.117 per mile. The same car in metric terms does 7.84 L/100 km. Entering a 450 km round trip at 7.5 L/100 km and 1.80 per litre instead: 900 km × 7.5 ÷ 100 = 67.5 L, cost 121.50; with three passengers that is 40.50 each.

Formulas and conversion factors

distance (km) = miles × 1.609344
L/100 km = 100 ÷ (km/L) = 235.214583 ÷ mpg (US) = 282.480936 ÷ mpg (UK)
fuel (L) = distance (km) × L/100 km ÷ 100
price per litre = price per gallon ÷ 3.785411784 (US) or ÷ 4.54609 (UK)
cost = fuel (L) × price per litre;   per person = cost ÷ passengers

The mile, the US gallon and the UK (imperial) gallon are defined exactly in SI units, so the constants above are exact to the digits shown (235.214583 = 100 × 3.785411784 ÷ 1.609344). The calculator does not add tolls, wear, parking or the extra consumption of a loaded car; treat the official consumption figure as a lower bound.

Sources: NIST Handbook 44 – Appendix C, general tables of units, US EPA – Fuel economy.

Questions

Is 1 mpg really 235 L/100 km?
Yes for US gallons: one US gallon is 3.785 litres and one mile is 1.609 km, so 1 mpg = 3.785 L per 1.609 km = 235.2 L per 100 km. For imperial gallons the constant is 282.5.
Which consumption figure should I enter?
Your own measured average (litres filled ÷ km driven × 100, or your trip computer) is best. Official WLTP or EPA figures are usually 10–20% optimistic for everyday driving.
Can I use it for an electric car?
Not directly – use the Electricity Cost Calculator with your car’s kWh/100 km instead, since the price is per kWh rather than per litre.