How the Trip Cost Is Calculated
The math is simple, and it helps to understand it. Your total gas cost comes from three things: how far you're driving, how efficient your car is, and what gas costs where you're filling up.
The formula is: (Trip miles ÷ your MPG) × gas price = total cost. First it works out how many gallons you'll burn (miles divided by MPG), then multiplies that by the price per gallon. That's it — no hidden steps.
What MPG Should You Enter?
Use your car's real number if you know it — it's often on the dashboard display. If not, here are rough averages to go by:
- Small sedans: 28–35 MPG
- Larger sedans / small SUVs: 24–30 MPG
- Full-size SUVs: 18–24 MPG
- Pickup trucks: 16–22 MPG
- Hybrids: 40–55 MPG
Keep in mind highway driving usually beats city driving on fuel economy, so a long road trip may do a little better than your everyday average.
A Few Ways to Cut Your Trip Cost
- Fill up in the cheapest state on your route — the difference between states can be over $1 a gallon. Check our live tracker before you leave.
- Keep your tires properly inflated; low pressure quietly eats your mileage.
- Use cruise control on the highway to hold a steady, efficient speed.
- Don't carry unnecessary weight or roof cargo — both drag your MPG down.
- See our full guide on saving money on gas for more.
Frequently Asked Questions
How do I calculate the gas cost of a road trip?
Divide your trip distance by your car's MPG to get gallons needed, then multiply by the price per gallon. Example: 500 miles ÷ 25 MPG = 20 gallons; at $4.00/gallon that's $80. This calculator does it for you automatically.
What MPG should I use?
Your car's real MPG if you know it. Otherwise: sedans 25–35, SUVs 20–28, trucks 18–24, hybrids 40–55. Highway driving is usually more efficient than city driving.
Does this use current gas prices?
Yes. Selecting a state fills in that state's price from live weekly EIA data where available. You can also type your own price if you know the exact local rate.