Fuel Cost Calculator

How to work out the fuel cost of a trip

Three numbers decide what a drive costs in fuel:

• Distance — from a map or route planner. Tick “Round trip” to count the way back.
• Fuel economy — how far your car goes on a unit of fuel. In the US it is quoted in miles per gallon (mpg); most other countries quote fuel consumption in litres per 100 kilometres (L/100 km). Your trip computer or fuel receipts give a better figure than the official rating.
• Fuel price — per gallon or per litre, from the pump you expect to use.

The calculator turns these into the fuel you’ll burn and what it costs, the cost per mile or kilometre, and each person’s share when you split it. With “Compare with another car” it prices the same trip for a second vehicle — handy when choosing which car to take or estimating the fuel savings of a more efficient one.

Switching between the two unit systems converts the numbers you entered rather than resetting them, so you can also use it to translate a European L/100 km figure into mpg.

Fuel cost formulas

Converting fuel economy between the two systems:

235.214583…

100 × 3.785411784 ÷ 1.609344: litres in a US gallon and kilometres in a mile, both exact by definition

mpg

miles per US gallon (the UK mpg uses the larger imperial gallon, so its figures are about 20% higher)

L/100 km

litres of fuel used per 100 kilometres; lower is better

Because L/100 km is the inverse of mpg, the savings from better economy are not linear in mpg: going from 20 to 25 mpg saves more fuel than going from 40 to 45 mpg over the same distance.

Worked example

A 300-mile drive in a car that gets 28 mpg, with gas at $3.50 a gallon:

1. Fuel needed: 300 ÷ 28 = 10.71 gallons
2. Fuel cost: 10.7143 × $3.50 = $37.50
3. Cost per mile: $37.50 ÷ 300 = $0.125
4. As a round trip shared by three people: 600 miles, $75.00 in total, $25.00 each.
5. A car that gets 40 mpg would use 7.5 gallons and cost $26.25 one way — $11.25 less.

In metric units, 500 km at 7 L/100 km with fuel at 1.80 a litre uses 500 × 7 ÷ 100 = 35 litres and costs 63.00.

Getting a realistic estimate

• Use your own economy figure. Official ratings come from standard test cycles. Divide the distance on your odometer by the fuel you put in at the next fill-up for your real number.
• Highway and city differ. Most cars use less fuel per mile at steady highway speeds than in stop-and-go traffic, and more again at high speed. Pick the figure that matches the trip.
• Fuel is only part of the cost of driving. Tolls, parking, maintenance and depreciation add to it. For the cost of owning the car itself, see the auto loan calculator.
• Converting units. For other distance or volume conversions, use the length converter or volume converter.