Calculate your gas cost for any trip or over a full year of driving.
The formula is straightforward: divide your total distance by your car's MPG to get the gallons needed, then multiply by the current gas price per gallon.
Fuel Cost = (Distance ÷ MPG) × Gas Price Per Gallon
For example: a 400-mile trip in a car that gets 28 MPG at $3.60/gallon costs about $51. The same trip in a 20 MPG truck costs $72. Over a year of commuting 15,000 miles, that $21 difference per trip compounds to $787 more annually for the truck driver.
Knowing your vehicle class helps you set realistic expectations and compare options. Compact and subcompact cars typically achieve 32–42 MPG combined. Mid-size sedans and crossovers land at 26–34 MPG. Full-size SUVs run 18–25 MPG depending on engine and drivetrain. Full-size pickup trucks average 18–24 MPG for gas engines, 20–28 MPG for diesel. Hybrid vehicles commonly reach 45–58 MPG. Plug-in hybrids running in EV mode can achieve 80–120 MPGe before switching to the gas engine.
Your real-world MPG depends significantly on how and where you drive. City driving typically yields 15–20% fewer miles per gallon than highway driving due to idling, frequent acceleration, and stop-and-go traffic. Your EPA window sticker shows separate city, highway, and combined estimates — use the combined figure for mixed driving and the highway figure for long trips.
To calculate your annual fuel spend, multiply your yearly miles by your cost per mile (gas price ÷ MPG). A driver putting 15,000 miles on a 30 MPG vehicle at $3.50/gallon spends $1,750 per year in gas. The same mileage in a 20 MPG vehicle costs $2,625 — $875 more per year. Over 5 years, that's $4,375 in additional fuel costs just for the lower-efficiency option.
This math is why fuel economy should factor heavily into vehicle purchase decisions, especially for high-mileage drivers. Each 5 MPG improvement saves a 15,000-mile/year driver roughly $350–$500 annually at current gas prices.
Gas prices fluctuate significantly — often $0.50–$1.00/gallon over the course of a year, with larger swings during supply disruptions. For a driver using 50 gallons per month, a $0.50/gallon increase adds $25/month or $300/year to fuel costs. A $1.00 spike adds $600/year. High-mileage drivers and those with lower-MPG vehicles feel these swings more acutely.
Use this calculator to run scenarios at different gas prices to understand how your monthly budget changes. If you're comparing vehicles to buy, running fuel cost projections at both current and elevated gas prices gives you a more conservative estimate of operating costs over the vehicle's life.
Tire pressure is the easiest win: under-inflated tires increase rolling resistance and reduce fuel economy by 0.5–3%. Check pressure monthly (tires naturally lose about 1 PSI per month) and keep them at the manufacturer's recommended PSI found on the door jamb sticker. Driving smoothly — anticipating stops and accelerating gradually rather than flooring it — can improve fuel economy by 10–40% in city driving.
Highway speed has a dramatic effect on efficiency. Most vehicles hit peak fuel economy around 50–60 mph. Each 5 mph above 60 reduces fuel economy by 5–7%. Driving 75 mph instead of 65 mph can cost you 10–15% more in fuel on a highway trip. Reducing your cruise control speed on long drives is one of the highest-leverage fuel-saving actions available.
Regular maintenance matters too: a clogged air filter can reduce MPG by 10%, and spark plug misfires reduce efficiency by 4–10%. Using the manufacturer-recommended motor oil grade instead of a heavier weight oil improves fuel economy by 1–2%. These are small margins individually, but combined they add up to meaningful savings over 15,000 annual miles.