A road trip rarely costs just the fuel. By the time you add tolls, parking, a few meals on the road and a share of the car's wear, the total can be well above the number on the gas pump. A good estimate before you leave helps you decide whether to drive or fly, how much to ask passengers to chip in, and what to budget. This trip cost calculator starts from the distance and your car's fuel economy and adds everything else you enter.
How to use the trip cost calculator
- Enter the distance in miles or kilometres, and choose one way or round trip.
- Enter your fuel economy in mpg, L/100 km or km/L, and the fuel price per gallon or litre.
- Add tolls and other costs such as parking or food.
- Set the number of people who share the cost.
- Read the total, the cost per person and the cost per mile.
To work only with fuel use the fuel cost calculator; to measure your own mpg after a fill-up, the gas mileage calculator; to switch between mpg and litres per 100 km, the fuel economy converter.
Trip cost formula
Fuel cost = fuel used × price per gallon
Total = fuel cost + tolls + other costs
Per person = total ÷ number of people
- Distance is doubled automatically for a round trip
- L/100 km converts to mpg with mpg = 235.215 ÷ (L/100 km)
- Cost per mile = total ÷ distance
Worked example: 500-mile trip
- Fuel used: 500 ÷ 25 = 20 gallons.
- Fuel cost: 20 × $3.50 = $70.
- Add tolls ($20) and parking ($10): total $100.
- Shared by two people: $50 each.
- Cost per mile: $100 ÷ 500 = $0.20.
Fuel needed per 100 miles
These rows are calculated from fuel use = 100 ÷ mpg; the last column converts the same economy to litres per 100 km.
| Fuel economy | Fuel per 100 miles | Cost at $3.50/gal | Cost at $4.50/gal | Same economy in L/100 km |
|---|---|---|---|---|
| 15 mpg | 6.67 gal | $23.33 | $30.00 | 15.7 L/100 km |
| 20 mpg | 5.00 gal | $17.50 | $22.50 | 11.8 L/100 km |
| 25 mpg | 4.00 gal | $14.00 | $18.00 | 9.4 L/100 km |
| 30 mpg | 3.33 gal | $11.67 | $15.00 | 7.8 L/100 km |
| 40 mpg | 2.50 gal | $8.75 | $11.25 | 5.9 L/100 km |
| 50 mpg | 2.00 gal | $7.00 | $9.00 | 4.7 L/100 km |
What the estimate leaves out
The result is only as accurate as the economy figure you use. Fuel use rises noticeably with speed; a roof box, a loaded trunk, strong headwinds, hills and air conditioning all push the figure up. If you have driven the route before, use the actual mpg from your trip computer. Fuel prices also vary along the way, so use an average for the route rather than your home price.
The “IRS business mileage rate” line puts the fuel-only cost in perspective. The rate for 1 July–31 December 2026 is 76 cents per mile — several times the fuel cost per mile for most cars — because it also includes depreciation, insurance, maintenance and repairs. If you want to know what a trip truly costs to your wallet rather than just the pump, the full-cost figure is the better comparison with a plane or train ticket.
For a business trip where you are reimbursed, the mileage reimbursement calculator gives the allowance directly. For a longer view of what a car costs per year, see the car ownership cost calculator.
Sources
Unit definitions: 1 US gallon = 3.785411784 litres and 1 mile = 1.609344 km (NIST). The IRS standard business mileage rates (76 cents per mile for 1 July–31 December 2026) come from the IRS “Standard mileage rates” page, collected 2026-10-09 in this site's data folder. Table values were computed from the formulas shown.
Frequently asked questions
How do I calculate the fuel cost of a trip?
Divide the distance by your fuel economy to get the fuel used, then multiply by the price: 500 miles ÷ 25 mpg = 20 gallons; at $3.50 per gallon that is $70.
Should I use my highway or combined mpg?
For a long highway trip use your real highway figure. Using the sticker highway number is optimistic if you carry a heavy load or drive fast; speed, wind and roof boxes lower mpg.
How is the cost per person worked out?
The total of fuel, tolls and other costs is divided evenly by the number of people sharing. Costs such as vehicle wear are not included unless you add them under other costs.
What is the IRS rate shown?
It is the IRS standard business mileage rate (76 cents per mile for 1 July–31 December 2026), shown for comparison. It covers fuel, depreciation, insurance and repairs, so it is much higher than fuel alone.
Can I use kilometres and litres?
Yes. Switch the distance unit to km, choose L/100 km or km/L for economy, and price per litre. The fuel result can be shown in gallons or litres.