Gas Cost Calculator
Find out how much gas will cost for a road trip, or how much you spend on fuel every month and year. Enter your miles, your car’s mpg and the gas price, and see the cost per mile, the cost per person and how much a price increase adds to your budget.
Fuel cost only. Real mpg varies with speed, traffic, weather and load, so treat results as estimates.
How to calculate gas cost
Gas cost depends on three numbers: how far you drive, how many miles your car goes on a gallon and what a gallon costs.
Example: a 300-mile trip in a car that gets 28 mpg uses 300 ÷ 28 = 10.71 gallons. At $4.35 a gallon, that is 10.71 × $4.35 = $46.61. Make it a round trip and the cost doubles to $93.21. Split between three friends, each pays about $31.07.
For your monthly budget, start with your daily drive. 30 miles a day, 5 days a week is 30 × 5 × 52 ÷ 12 = 650 miles a month. Add 200 miles of errands and weekend driving, and you drive about 850 miles a month. At 28 mpg and $4.35, that is about $132 a month, or $1,585 a year.
Road trip gas costs at today’s prices
One-way fuel cost at the October 5, 2026 U.S. average of $4.354 a gallon:
| Trip | Distance | 20 mpg | 25 mpg | 30 mpg | 40 mpg |
|---|---|---|---|---|---|
| Short day trip | 100 miles | $21.77 | $17.42 | $14.51 | $10.88 |
| Weekend getaway | 250 miles | $54.43 | $43.54 | $36.28 | $27.21 |
| Long road trip | 500 miles | $108.85 | $87.08 | $72.57 | $54.43 |
| Cross-state drive | 1000 miles | $217.70 | $174.16 | $145.13 | $108.85 |
Fuel cost per mile by mpg and gas price
Use this table to see what each mile costs you in fuel. Multiply by your yearly miles for a quick yearly estimate.
| Fuel economy | $3.00 | $3.50 | $4.00 | $4.35 | $5.00 | $6.00 |
|---|---|---|---|---|---|---|
| 15 mpg | 20.0¢ | 23.3¢ | 26.7¢ | 29.0¢ | 33.3¢ | 40.0¢ |
| 20 mpg | 15.0¢ | 17.5¢ | 20.0¢ | 21.7¢ | 25.0¢ | 30.0¢ |
| 25 mpg | 12.0¢ | 14.0¢ | 16.0¢ | 17.4¢ | 20.0¢ | 24.0¢ |
| 30 mpg | 10.0¢ | 11.7¢ | 13.3¢ | 14.5¢ | 16.7¢ | 20.0¢ |
| 35 mpg | 8.6¢ | 10.0¢ | 11.4¢ | 12.4¢ | 14.3¢ | 17.1¢ |
| 40 mpg | 7.5¢ | 8.8¢ | 10.0¢ | 10.9¢ | 12.5¢ | 15.0¢ |
| 50 mpg | 6.0¢ | 7.0¢ | 8.0¢ | 8.7¢ | 10.0¢ | 12.0¢ |
Going from a 20 mpg vehicle to a 40 mpg one cuts your fuel cost per mile in half. At $4.35 a gallon and 12,000 miles a year, that is about $1,305 a year instead of $2,610.
Gas prices right now
The U.S. Energy Information Administration reported a national average of $4.354 a gallon for regular gasoline on October 5, 2026, about $1.23 more than a year earlier. Diesel averaged $6.199. Prices vary by region: about $3.91 on the Gulf Coast, $5.73 on the West Coast and about $6.23 in California.
Prices are high because crude oil is expensive, with Middle East supply constrained in 2026. The EIA expects gasoline to average just under $3.60 a gallon in 2027 if supply improves. For the full picture, including what higher prices mean for groceries, interest rates and your budget, read our guide: Gas Prices Above $4 in 2026: What $100 Oil Means for Your Budget.
Simple ways to spend less on gas
- Compare stations. Prices often differ by 30 cents or more a gallon within a few miles. On a 15-gallon tank, that is $4.50 a fill-up.
- Drive smoothly. Hard acceleration and speeds well above 50 mph lower your mpg. Cruise control on the highway helps.
- Keep tires inflated and remove heavy items you don’t need from the trunk.
- Combine errands into one loop instead of several short trips from a cold start.
- Budget for today’s price. Put your monthly fuel cost in your budget so it doesn’t end up on a credit card. The savings goal calculator helps you set money aside for a road trip.
Shopping for a car? Fuel is only part of the cost. Compare monthly payments with the auto loan calculator.
Frequently asked questions
How do you calculate gas cost for a trip?
Divide the trip distance by your car's miles per gallon to get the gallons you need, then multiply by the price per gallon. For a 300-mile trip in a car that gets 28 mpg with gas at $4.35, that is 300 ÷ 28 = 10.7 gallons, and 10.7 × $4.35 = about $46.61.
How much does it cost to drive one mile?
Divide the price of gas by your mpg. At $4.35 a gallon, a car that gets 25 mpg costs about 17.4 cents a mile in fuel, and one that gets 40 mpg costs about 10.9 cents. That covers fuel only, not maintenance, insurance or wear.
How much do I spend on gas a month?
Multiply the miles you drive each month by the price per gallon and divide by your mpg. Driving 30 miles a day, 5 days a week is about 650 miles a month. At 25 mpg and $4.35 a gallon, that is about 26 gallons, or roughly $113 a month.
What is the average gas price right now?
The U.S. Energy Information Administration's national average for regular gasoline was $4.354 a gallon on October 5, 2026, about $1.23 higher than a year earlier. Prices vary widely by state, from about $3.91 on the Gulf Coast to about $6.23 in California.
How do I find my car's real mpg?
Fill the tank, reset your trip odometer, drive normally until your next fill-up, then divide the miles driven by the gallons it took to refill. Your real mpg is often lower than the window-sticker number in city driving, cold weather or at highway speeds above about 50 mph.
This calculator gives estimates of fuel cost only. Actual fuel use depends on your vehicle, driving style, traffic, terrain and weather. Gas prices are from the U.S. Energy Information Administration’s weekly fuel survey and change every week.