Gas trip calculator
A 300-mile drive in a car that gets 30 MPG takes 10 gallons of gas. At the U.S. average of $3.995 a gallon (EIA, week of November 9, 2026), that is $39.95 one way or $79.90 round trip.
On this page (10 sections)
How to use the calculator
- Distance. Enter the miles from a map app. Pick one way or round trip.
- MPG. Type your car’s miles per gallon, or pick the car to use its EPA rating. Your own MPG from the MPG calculator is usually closer to real life.
- Gas price. Use the price per gallon where you will fill up. The form starts at the latest U.S. average from the EIA.
- Tolls and people (optional). Add the total tolls and the number of people who share the cost.
The result shows the gallons you need, the gas cost, the total with tolls, and each person’s share.
The formula: gallons and cost
- Gallons needed = miles ÷ MPG
- Gas cost = gallons × price per gallon
- Cost per person = (gas cost + tolls) ÷ people
Example: 300 miles ÷ 30 MPG = 10 gallons. 10 gallons × $3.995 = $39.95. For a different split, such as one friend who rides only half the way, use the gas money calculator.
Gallons needed and fill-ups
Gallons per mile is MPG turned upside down: 1 ÷ MPG. A 30 MPG car uses 1 ÷ 30 = 0.033 gallons per mile, so 300 miles takes 10 gallons. A 20 MPG car uses 0.05 gallons per mile and needs 15 gallons for the same drive.
To see how many times you will stop for gas, multiply your tank size by your MPG to get your range. A 14-gallon tank at 30 MPG goes about 420 miles on a full tank. Plan stops well before empty, since your real MPG on the trip can be lower than usual. Your tank size is in your owner’s manual.
Round trip
A round trip is the one-way distance times 2. In the example, 600 miles takes 20 gallons and costs $79.90. If you take a different road back, or plan side trips at your destination, add those miles to the total instead of doubling.
Tolls
The calculator does not look up tolls. Toll prices depend on the road, the time of day, your vehicle, and whether you pay with a transponder or by mail. Check the toll road’s own website or your map app for the trip, then type the total. Example: $79.90 in gas plus $15 in tolls is $94.90; split among 4 people, that is $23.73 each.
Gas cost by car: EPA MPG vs your MPG
When you pick a car, the calculator uses its EPA combined MPG from fueleconomy.gov. EPA numbers come from laboratory tests run under the same conditions for every car, so they are good for comparing cars. They cannot predict every driver’s mileage. Your MPG on a trip depends on how you drive:
- Speed and style. Aggressive driving (fast starts, hard braking, speeding) can lower gas mileage by roughly 15%–30% at highway speeds, according to fueleconomy.gov.
- Air conditioning. Running the AC on max can reduce MPG by roughly 5%–25%.
- Cold weather. At 20 °F, a gas car’s city MPG can be about 15% lower than at 77 °F.
- Load. An extra 100 pounds can cut MPG by about 1%. Cargo on the roof adds drag on top of that.
For a trip with a full car and highway speeds, using an MPG a little below your usual number gives a safer budget. To learn your real number, see how to calculate MPG.
Gas cost for popular distances
| Distance | 25 MPG: gallons | 25 MPG: cost | 30 MPG: gallons | 30 MPG: cost |
|---|---|---|---|---|
| 100 miles | 4 | $15.98 | 3.3 | $13.32 |
| 250 miles | 10 | $39.95 | 8.3 | $33.29 |
| 500 miles | 20 | $79.90 | 16.7 | $66.58 |
| 1,000 miles | 40 | $159.80 | 33.3 | $133.17 |
| 2,000 miles | 80 | $319.60 | 66.7 | $266.33 |
| 3,000 miles | 120 | $479.40 | 100 | $399.50 |
Price: U.S. average retail price of regular gasoline, $3.995 per gallon, week of November 9, 2026 (EIA). Prices vary by state and by station; enter your own in the calculator.
To compare cars or budgets by the mile instead of by trip, use the fuel cost per mile calculator.
Common mistakes
- Doubling twice. If you enter the round-trip distance, keep the switch on one way.
- Using the city or highway number alone. Most trips mix both. The combined MPG, or your own measured MPG, is a better fit.
- Forgetting local driving. Miles around town at your destination add up. Add them to the distance.
- Old gas prices. Prices change every week. Check the price near your route.
Before a long drive, it also helps to check the tires, fluids, and lights. Our car maintenance checklist has a short road trip section.
FAQ
How much gas will I need for my trip?
Divide the miles by your car’s MPG. A 450-mile trip in a 30 MPG car needs 15 gallons. If your trip has steep hills, a full load, or lots of highway speed, plan for a little more.
How do I figure gas cost for a round trip?
Double the one-way miles, divide by MPG, and multiply by the gas price. For 300 miles each way at 30 MPG and $3.995 a gallon: 600 ÷ 30 = 20 gallons, and 20 × $3.995 = $79.90.
How much does it cost to drive 1,000 miles?
At the U.S. average of $3.995 a gallon (EIA, week of November 9, 2026), about $133 in a 30 MPG car and about $160 in a 25 MPG car. That is gas only, not tolls, parking, or wear on the car.
What gas price should I enter?
The price where you expect to fill up. If you are crossing several states, an average of the prices along the way works well. The U.S. average is a reasonable starting point when you don’t know.
Does the calculator add tolls for me?
No. Toll rates change by road, time, and payment method, so we don’t guess them. Look up the tolls for your route and enter the total; the calculator adds it to the cost and splits it with the gas.
Sources
- U.S. Energy Information Administration (EIA), Gasoline and Diesel Fuel Update, U.S. regular gasoline, week of November 9, 2026 (checked November 12, 2026): eia.gov
- fueleconomy.gov (U.S. DOE and EPA), How vehicles are tested: fueleconomy.gov
- fueleconomy.gov, Factors that affect MPG (AC, aggressive driving): fueleconomy.gov
- fueleconomy.gov, Driving more efficiently (extra weight): fueleconomy.gov
- fueleconomy.gov, Fuel economy in cold weather: fueleconomy.gov