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Gas Cost Calculator for a Road Trip
What your road trip costs in gas and what each person pays
Use this gas cost calculator to see how many gallons your road trip will use based on your car's miles per gallon, what it costs at the price you type, and how much each person owes.
The key idea
The mpg on the sticker is not your mpg: it is only a starting point
600 miles in a car that gets 30 mpg is 20 gallons: at $3.50 a gallon, $70. If your car really gets 25 mpg on the highway, the same trip takes 24 gallons and costs $84. Getting 5 mpg less makes the trip 20% more expensive.
How it is calculated
Gallons = miles / mpg Cost = gallons × price per gallon
Your real fuel economy depends on speed, load, air conditioning and the road; at high highway speeds it is often lower than the rating. Tolls and parking are not included.
Worked example
600 miles at 30 mpg with gas at $3.50 a gallon: 20 gallons and $70.00. Split among 3 people, $23.33 each. That is $11.67 per 100 miles.
Official sources
- FuelEconomy.gov (U.S. Department of Energy and EPA) · EPA fuel economy ratings
Typical cases
Gas cost per 100 miles by mpg and gas price
What 100 miles of driving costs in gas by your car's fuel economy and the price per gallon. For a 300-mile trip, multiply by three.
| Fuel economy | $3.00/gal | $3.50/gal | $4.00/gal | $5.00/gal |
|---|---|---|---|---|
| 15 mpg | $20.00 | $23.33 | $26.67 | $33.33 |
| 20 mpg | $15.00 | $17.50 | $20.00 | $25.00 |
| 25 mpg | $12.00 | $14.00 | $16.00 | $20.00 |
| 30 mpg | $10.00 | $11.67 | $13.33 | $16.67 |
| 35 mpg | $8.57 | $10.00 | $11.43 | $14.29 |
| 40 mpg | $7.50 | $8.75 | $10.00 | $12.50 |
| 50 mpg | $6.00 | $7.00 | $8.00 | $10.00 |
Save or share this table as an image Common questions
Frequently asked questions
How do I calculate the gas cost of a trip?
Divide the miles by your car's mpg to get gallons, then multiply the gallons by the price per gallon. 600 miles at 30 mpg is 20 gallons; at $3.50 a gallon, that is $70.
How do I find my car's real mpg?
Use a full tank: fill up, reset the trip odometer, and at the next fill-up divide the miles driven by the gallons you pumped. To compare, check your car's EPA rating on FuelEconomy.gov.
What gas price should I use?
The price at the station where you plan to fill up, for the grade your car needs (regular, midgrade, premium or diesel). Prices change from state to state and station to station, so check before you leave.
Are tolls included?
No: the calculator only counts gas. If your route has tolls or paid parking, add them separately and split them among the people in the car.
How should we split gas among passengers?
The simplest way is to divide the total by everyone, driver included. That is what the per-person figure shows; set People to the number of riders who are splitting it.
Does a car get worse mileage on the highway?
At high speeds, yes: air resistance rises quickly with speed and fuel economy drops. Heavy loads, air conditioning and hills also lower it.
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