Fuel Cost Calculator

How this is worked out

With litres and kilometres the arithmetic is direct, which is the whole argument for the metric measure:

litres = distance in km × L/100km ÷ 100

cost = litres × price per litre

400 km at 9.0 L/100km is exactly 36 litres, and at $1.55 a litre that is $55.80 — 13.95 cents a kilometre. Split four ways it is $13.95 each. No conversion factor appears anywhere, because the units already agree.

The conversions only become necessary when reading numbers from elsewhere, and then two of them are needed at once. 9.0 L/100km is 26.1 MPG (US) and 31.4 MPG (imperial) — the same car, three numbers, because the American and British gallons differ by 20.1%.

MPG (US) = 235.215 ÷ (L/100km) · MPG (imperial) = 282.481 ÷ (L/100km)

Those constants come from the exact definitions: 3.785411784 litres to a US gallon, 4.54609 to an imperial one, 1.609344 km to a mile.

A worked example

Lower is better, and that is not a trivial difference

L/100km measures fuel per distance, so a smaller number is a better car. MPG measures distance per fuel, so a bigger number is better. They are reciprocals, and the practical consequence is that L/100km is the scale on which equal differences mean equal amounts of fuel and MPG is not.

Over 15,000 km a year, going from 10 to 8 L/100km saves 300 litres. Going from 6 to 5 L/100km — a bigger proportional improvement — saves 150 litres, half as much. On the MPG scale the same two changes look like "+5.9 MPG" and "+7.8 MPG", which points the wrong way entirely.

This is why fuel savings from replacing a thirsty vehicle are always larger than the equivalent-looking improvement at the efficient end, and why the comparison panel on this page prices both vehicles in dollars rather than asking you to judge two economy figures.

Reading American numbers without importing the error

Most car content Canadians read is American, and it is in MPG — specifically MPG (US). British content uses MPG (imperial), which is 20.1% larger for the same car. The word is the same, the abbreviation is the same, and the numbers differ by a fifth.

A car rated 9.0 L/100km here is 26.1 MPG in an American review and 31.4 MPG in a British one. If you compare a Canadian L/100km rating against a British MPG figure without converting, you will conclude that a car sold on both sides of the Atlantic is meaningfully more efficient in Britain. It is not; the gallon is.

The four-unit table under the result converts whatever you enter into all four at once, so a spec sheet in any of them can be checked against your own figure directly.

Winter, and why your rating is optimistic from November

Natural Resources Canada ratings come from a five-cycle laboratory test that includes cold-temperature and air-conditioning cycles, which makes them more realistic than a simple city/highway pair. They are still an average, and a Canadian winter is not average.

Cold engines run rich until they warm up, which on a short trip may be most of the trip. Winter tires add rolling resistance, block heaters and remote starters burn fuel before you move, snow and slush add drag, and cabin heat in a modern efficient engine sometimes has to be generated rather than scavenged. A 15–30% winter penalty on short urban trips is entirely normal, and hybrids and EVs lose proportionally more.

The way to hold this honestly is to measure your own consumption over a winter month and a summer month and enter each. Most trip computers will do it for you; the odometer and the pump receipts will do it more accurately.

Cost per kilometre, and what fuel leaves out

Fourteen cents a kilometre in fuel is a useful number for deciding whether to take one car or two, or whether a detour to cheaper fuel pays for itself. It is not the cost of driving a kilometre. Depreciation, insurance, maintenance, tires — including a second set for winter — and licensing usually add up to several times the fuel figure.

Provincial differences make the fuel component itself less comparable than it looks. Provincial fuel taxes differ, carbon pricing has differed by province and over time, and remote and northern communities pay substantially more than the cities. A national average price is not the price at your station, which is why this page asks for yours.

For a genuine per-kilometre cost of ownership, add insurance, maintenance and depreciation to the fuel figure here. For deciding what a specific drive costs, the fuel figure is the right one, and it is the one this page computes.

Assumptions and sources

US gallon

3.785411784 litres exactly (231 cubic inches).

Imperial gallon

4.54609 litres exactly, giving the 20.1% gap between the two MPG scales.

Mile

1.609344 kilometres exactly, international yard and pound agreement 1959.

Conversion constants

MPG (US) = 235.215 ÷ L/100km; MPG (imperial) = 282.481 ÷ L/100km. Both derived from the exact definitions above rather than tabulated.

Fuel price

The default here is a PLACEHOLDER, not a researched figure. Prices move weekly and differ by province because provincial taxes and carbon pricing differ.

Consumption ratings

Natural Resources Canada five-cycle test ratings. https://natural-resources.canada.ca/energy-efficiency/transportation-alternative-fuels/fuel-consumption-guide

Arithmetic

tripCost, annualFuel and efficiencyIn in assets/js/tools/work.js, verified in tools/test/work.mjs.