How to use this fuel cost calculator
Enter the one-way distance of your trip and choose one way or round trip. Add your car's fuel economy and the current price of fuel where you'll be filling up. If friends or family are sharing the ride, set the number of people to see each person's share.
Not sure of the distance? A map app shows it for any route. For fuel economy, use your car's official combined figure, or better, measure the real number with our MPG calculator. Highway driving usually beats the combined figure, while city traffic, heavy loads, roof boxes and high speeds make it worse.
The fuel cost formula
Fuel cost = distance ÷ fuel economy × price per gallon
In metric countries, fuel economy is given in liters per 100 km, so the formula becomes: fuel cost = distance × (L/100 km) ÷ 100 × price per liter.
Worked example: a 300-mile drive in a car that gets 30 mpg uses 300 ÷ 30 = 10 gallons. At $3.50 a gallon, that's $35 one way, or $70 for the round trip. Split between two people, each pays $35 for the whole trip.
How speed changes your fuel cost
Aerodynamic drag rises steeply with speed, and the U.S. Department of Energy notes that fuel economy usually drops quickly above about 50 mph. On a long highway trip, slowing from 75 to 65 mph can cut fuel use by roughly 10–15%, which often saves more than hunting for cheaper fuel.
| Fuel economy | Fuel for 300 miles | Cost at $3.50/gal |
|---|---|---|
| 20 mpg (11.8 L/100 km) | 15 gal | $52.50 |
| 25 mpg (9.4 L/100 km) | 12 gal | $42.00 |
| 30 mpg (7.8 L/100 km) | 10 gal | $35.00 |
| 40 mpg (5.9 L/100 km) | 7.5 gal | $26.25 |
| 50 mpg (4.7 L/100 km) | 6 gal | $21.00 |
Ways to spend less on fuel
- Keep tires at the recommended pressure, shown on the sticker inside the driver's door.
- Remove roof racks and boxes when you aren't using them. They add drag at highway speeds.
- Use cruise control on the highway and accelerate gently; hard acceleration and braking waste fuel.
- Compare prices along the route. Fuel near highway exits and in city centers often costs more than a few minutes away.
Thinking of going electric? Our EV charging cost calculator compares the same trip in an electric car.
Frequently asked questions
How do I calculate gas cost for a trip?
Divide the distance by your car's miles per gallon to get the gallons needed, then multiply by the price per gallon. For example, 300 miles ÷ 30 mpg = 10 gallons, and 10 × $3.50 = $35.
How much gas does it take to drive 100 miles?
Divide 100 by your mpg. A car that gets 25 mpg uses 4 gallons per 100 miles; at $3.50 a gallon that's $14. A 40 mpg car uses 2.5 gallons, or $8.75.
How should we split gas money on a road trip?
The simplest fair way is to divide the total fuel cost by the number of people. Some groups also give the driver a share-free trip, or split tolls and parking the same way.
How much CO₂ does a gallon of gas produce?
Burning one gallon of gasoline releases about 8.9 kg (19.6 lb) of carbon dioxide, according to the U.S. EPA. That's about 2.35 kg per liter. Diesel produces a little more, about 10.2 kg per gallon.
Results are estimates. Real fuel use depends on speed, traffic, weather, load and how the car is driven.