Gas Calculator - Trip Fuel Cost Estimator
Enter your trip distance, vehicle fuel economy and local gas price to instantly see how much you will spend on fuel. The calculator works in miles/gallons or kilometres/litres, handles one-way or round trips, and also shows gallons consumed, cost per mile and monthly gas spending at your typical mileage. Results update as you type.
How gas cost is calculated
The core formula is straightforward: Fuel Cost = (Distance / MPG) x Gas Price. For a 200-mile trip in a car rated 28 MPG with gas at $3.45 per gallon, you need 200 / 28 = 7.14 gallons, and the cost is 7.14 x $3.45 = $24.63. In metric, the equivalent is: Fuel = (Distance in km / 100) x L/100 km, then Cost = Litres x Price per litre. Every output on this page flows directly from those two equations, so you can verify the math step by step using the "Show your work" panel.
Why MPG (or L/100 km) matters more than gas price
Many drivers focus on finding the cheapest gas station, but vehicle fuel economy has a larger long-term effect on what you pay. A vehicle that gets 40 MPG costs $1,035 per year at 12,000 miles and $3.45/gal. A vehicle at 20 MPG costs $2,070 - double - regardless of where you fill up. A $0.20/gal price difference on 400 gallons saved is only $80 per year, while moving from 25 to 35 MPG saves over $470 per year on the same mileage. Use the reference table above to benchmark your vehicle's economy against its class average.
Tips to reduce your fuel bill on any trip
Maintain steady highway speeds: fuel consumption rises sharply above 60 mph (97 km/h). Keep tires inflated to the pressure on the door jamb sticker - underinflated tires add up to 3 percent to fuel use. Avoid idling for more than 30 seconds (a modern engine restarts on almost no fuel). Use cruise control on flat highways to eliminate creep above your target speed. Remove roof racks and cargo carriers when not in use - they add aerodynamic drag of 5 to 10 percent. Use the manufacturer-recommended oil grade, which can improve economy by 1 to 2 percent. For city trips, plan routes to combine errands and avoid left turns, which add idle time.
Round trips, carpooling and cost sharing
Select "Round trip" to automatically double the distance and get the total cost for there-and-back. To calculate per-person cost for a carpool, divide the total trip cost by the number of passengers. For regular commuters, the monthly and annual estimates let you track fuel as a budget line item and compare it against alternatives like public transit or remote work. If you drive for work or rideshare, the cost-per-mile output is the number you need for reimbursement claims or profitability analysis - the 2025 IRS standard mileage rate for business is 70 cents per mile, which covers fuel plus depreciation and insurance.
Typical fuel economy by vehicle type (US EPA estimates)
| Vehicle type | Typical MPG | Litres/100 km | Annual fuel cost (12,000 mi at $3.45/gal) |
|---|---|---|---|
| Compact car | 32-40 MPG | 5.9-7.4 | $1,035-$1,294 |
| Mid-size sedan | 27-35 MPG | 6.7-8.7 | $1,183-$1,533 |
| Full-size sedan | 22-30 MPG | 7.8-10.7 | $1,380-$1,882 |
| Small SUV / crossover | 25-32 MPG | 7.4-9.4 | $1,294-$1,656 |
| Mid-size SUV | 20-28 MPG | 8.4-11.8 | $1,479-$2,070 |
| Full-size SUV / truck | 14-22 MPG | 10.7-16.8 | $1,882-$2,957 |
| Hybrid (compact) | 48-58 MPG | 4.1-4.9 | $714-$863 |
| Plug-in hybrid | 35-50 MPG | 4.7-6.7 | $828-$1,183 |
Combined city/highway averages. Actual economy varies by model year, driving conditions and maintenance.
Frequently asked questions
How do I calculate how much gas I will need for a trip?
Divide the trip distance by your vehicle's MPG rating. For example, a 300-mile trip in a 30 MPG car needs 300 / 30 = 10 gallons. Multiply by the gas price to get the total cost. In metric, multiply (km / 100) by L/100 km to get the litres needed.
Where can I find my car's MPG rating?
The easiest sources are the window sticker from when the vehicle was new, the EPA's fueleconomy.gov database (searchable by year, make and model), or your car's trip computer if it has one. City and highway ratings differ by 20 to 40 percent on most vehicles - use the combined rating for mixed driving, the highway rating for road trips.
Does the calculator account for city vs. highway driving?
The calculator uses whatever fuel economy figure you enter. For best accuracy, use the EPA highway MPG rating for long highway trips, the city rating for stop-and-go urban driving, or the combined rating for a mix. Your real-world economy may be 10 to 20 percent below the EPA estimate depending on driving style, temperature and load.
How do I convert L/100 km to MPG?
Use the formula: MPG = 235.215 / (L/100 km). For example, 8 L/100 km = 235.215 / 8 = 29.4 MPG. The calculator handles this conversion internally when you switch between unit systems.
What is the average MPG of a US passenger car in 2025?
The EPA fleet average for new passenger cars was approximately 32 MPG in 2024-2025, while the combined fleet average including light trucks and SUVs was around 26-28 MPG. If you drive an older vehicle, your actual economy is likely lower - older models from the 2000s often rated 20-25 MPG combined.
How much does a road trip really cost in gas?
At $3.45/gal and 28 MPG (rough US averages), a 500-mile road trip costs about $61.60 in fuel. A 1,000-mile trip costs around $123. Long-haul trips in a truck or full-size SUV at 18 MPG cost about $96 for 500 miles and $191 for 1,000 miles at the same price. Enter your actual vehicle and local price for a precise figure.