Budget your next drive
A road trip, a weekend visit or a regular carpool: knowing the cost of a drive helps you compare with flying or the train, split costs fairly and plan your budget. This calculator estimates the gallons you will burn, the total trip cost including tolls, the cost per person and the CO₂ emitted.
The formulas
- Total miles = one-way distance × 2 for a round trip.
- Gallons = total miles ÷ mpg.
- Fuel cost = gallons × price per gallon.
- Trip cost = fuel cost + tolls and parking for each leg.
- Cost per person = trip cost ÷ number of people sharing.
Worked example: a 300-mile trip and back
A car that gets 28 mpg, gas at $3.25 a gallon, $12 of tolls each way, two people.
- Total distance: 300 × 2 = 600 miles.
- Fuel: 600 ÷ 28 ≈ 21.4 gallons.
- Fuel cost: 21.4 × 3.25 ≈ $69.64.
- Tolls: 12 × 2 = $24.
- Trip cost: $93.64, or $46.82 per person.
- Emissions: 21.4 × 19.6 ≈ 420 lb of CO₂.
How fuel economy changes the cost (same trip)
| Fuel economy | Gallons | Fuel cost | Trip cost | Per person |
|---|---|---|---|---|
| 18 mpg | 33.3 | $108.33 | $132.33 | $66.17 |
| 22 mpg | 27.3 | $88.64 | $112.64 | $56.32 |
| 28 mpg | 21.4 | $69.64 | $93.64 | $46.82 |
| 35 mpg | 17.1 | $55.71 | $79.71 | $39.86 |
| 45 mpg | 13.3 | $43.33 | $67.33 | $33.67 |
| 55 mpg | 10.9 | $35.45 | $59.45 | $29.73 |
Getting a realistic mpg
EPA ratings are a good starting point, but real-world economy depends on how and where you drive. Highway driving at 75–80 mph can cut mpg by 15% or more compared with 60 mph. A loaded car, a roof box, air conditioning and headwinds all add fuel. For a reliable number, fill the tank, drive, then divide the miles driven by the gallons it takes to fill up again.
Ways to spend less on gas
- Slow down a little: most cars are most efficient around 50–60 mph.
- Drive smoothly: hard acceleration and braking can lower mileage by 15–30% on the highway.
- Check tire pressure monthly and before a long, loaded trip.
- Use apps to compare prices: stations near highway exits often charge more than those a mile away.
- Carpool: each extra person cuts the cost and emissions per person.
UK and metric drivers
In the UK, mpg is measured in imperial gallons (4.546 L), so multiply UK mpg by 0.833 before entering it, and enter the price per US gallon (price per liter × 3.785). Elsewhere, the calculator shows the equivalent liters per 100 km, which you can compare with your car’s official rating.
What about an electric car?
A typical EV uses about 30 kWh per 100 miles. Charging at home at $0.17 per kWh, the 600-mile trip would cost roughly $31 in electricity, before any fast-charging premium on the road.