# Fuel cost and trip planner Distance, your car's economy, and today's pump price. Any combination of units. Trip fuel cost is the distance divided by fuel economy, multiplied by the price per litre or gallon. The cost is shown in whatever currency you entered the price in. Real consumption moves with traffic, terrain, load and driving style, so treat this as a planning figure rather than a quote. ## The calculation ``` fuel needed = distance ÷ fuel economy cost = fuel needed × price per unit ``` Everything is converted to kilometers and litres internally, so you can mix units freely — a distance in miles, an economy in km/L and a price per gallon will still give the right answer. ## Why your real cost will differ A steady motorway cruise can beat the official rating; city traffic, mountains, a roof box or a full load of passengers will all miss it. Cold weather is the most underestimated factor — a short winter journey where the engine never fully warms up can use a third more fuel than the same trip in summer. For budgeting, take the number this calculator gives you and add 10 to 15%. You will rarely be caught short. ## Cutting the number down - Speed is the biggest lever on a long drive. Drag rises with the square of speed, so 110 km/h instead of 130 uses noticeably less fuel over the same distance. - Take the roof box off when you are not using it. Empty racks can cost several percent. - Check tyre pressures before a long trip, when the tyres are cold. - On a route with a choice, the slightly longer motorway option often uses less fuel than the shorter route through towns. Not sure what economy figure to enter? Measure it with the mileage calculator first. ## Next steps - [measure your real fuel economy](https://www.kilometer-mileage.com/mileage-calculator.html) - [convert the tank volume to gallons](https://www.kilometer-mileage.com/litres-to-gallons.html) - [why your actual spend will differ](https://www.kilometer-mileage.com/disclaimer.html) ## Common questions