How the Fuel Cost Calculator Works
Before a road trip it helps to know what the fuel will cost. The cost depends on three things: how far you go, how much fuel your vehicle uses for each mile or kilometer, and the price of the fuel. The Fuel Cost Calculator puts them together, and it can also share the cost between the people in the car.
What you enter
- The distance, in miles or in kilometers.
- The trip: one way, or a round trip (there and back), which doubles the distance.
- The fuel economy: in miles per gallon (mpg), or, in the metric mode, in liters per 100 km.
- The price of one gallon or one liter.
- The number of people that share the cost.
The formulas
US units: fuel (gallons) = distance (miles) / miles per gallon Metric units: fuel (liters) = distance (km) x liters per 100 km / 100 cost = fuel x price of one gallon (or liter) cost per person = cost / number of people
Worked example: 300 miles at 25 mpg
| Step | Calculation | Result |
|---|---|---|
| Fuel needed | 300 / 25 | 12 gallons |
| Cost at $3.50 a gallon | 12 x 3.50 | $42.00 |
| Cost per mile | 42 / 300 | $0.14 |
| Round trip | 600 miles, 24 gallons | $84.00 |
| Round trip shared by 3 people | 84 / 3 | $28.00 each |
Metric example
A trip of 480 km in a car that uses 9.4 liters per 100 km, with fuel at $1.50 a liter: fuel = 480 x 9.4 / 100 = 45.12 liters, and the cost is 45.12 x 1.50 = $67.68, or about $14.10 for every 100 km.
Chart: the same trip at different fuel prices
300 miles at 25 mpg. Each block is about $1.50. The price that you enter is green.
$3.00 ████████████████████████ $36.00 $3.50 ████████████████████████████ $42.00 $4.00 ████████████████████████████████ $48.00 $4.50 ████████████████████████████████████ $54.00 $5.00 ████████████████████████████████████████ $60.00
Every 50 cents on the price of a gallon adds $6 to this trip.
Chart: the cost of different distances
At 25 mpg and $3.50 a gallon, the cost grows in a straight line with the distance. Each block is about $3.50.
100 mi ████ $14.00 250 mi ██████████ $35.00 500 mi ████████████████████ $70.00 750 mi ██████████████████████████████ $105.00 1000 mi ████████████████████████████████████████ $140.00
Table: the same trip at other fuel economies
300 miles with fuel at $3.50 a gallon. The calculator draws a bar chart like this for your trip.
| Fuel economy | Liters per 100 km | Gallons | Cost |
|---|---|---|---|
| 15 mpg | 15.68 | 20.0 | $70.00 |
| 20 mpg | 11.76 | 15.0 | $52.50 |
| 25 mpg | 9.41 | 12.0 | $42.00 |
| 30 mpg | 7.84 | 10.0 | $35.00 |
| 40 mpg | 5.88 | 7.5 | $26.25 |
| 50 mpg | 4.70 | 6.0 | $21.00 |
A vehicle that does 40 mpg spends $26.25 on this trip, while one that does 15 mpg spends $70.00, which is more than 2.5 times as much.
Chart: sharing the cost
A round trip of 600 miles costs $84.00. Each block is about $2.10.
1 person ████████████████████████████████████████ $84.00 2 people ████████████████████ $42.00 3 people █████████████ $28.00 4 people ██████████ $21.00 5 people ████████ $16.80
Tips to lower the cost
- Drive at a steady speed. Fuel use rises fast above about 55 mph (90 km/h).
- Check the tire pressure and take out heavy things that you do not need.
- Use your real mileage. Find it with the Gas Mileage Calculator, because the number on the sticker is a test result.
- Compare prices along the way. Fuel is often cheaper away from highways.
- Share the ride. The fuel for the car is the same for one person or for four.
What this calculator does not include
- Traffic, hills, cold weather, air conditioning and a roof rack, which all raise the fuel use.
- Tolls, parking, ferries and the wear on the car.
- Changes in the price of fuel during the trip.
- Electric cars, which use kilowatt-hours and not gallons.
This tool gives an estimate for planning. Your real cost depends on your driving and on the roads.