Gas Cost Calculator for Road Trips
Miles, MPG and your gas price in. Gallons, total cost and cost per person out. Free, no sign-up.
Short answer
Gas cost = miles ÷ MPG × price per gallon. Example: 300 miles at 25 MPG and $3.50/gal = 12 gallons = $42.00.
The prefilled values are examples, not a current price. Enter what you pay near you.
Total gas cost
$42.00
Cost per person (1)
$42.00
Gallons used
12
Cost per mile
$0.14
300 mi ÷ 25 MPG = 12 gallons × $3.50 = $42.00
Your gas cost vs the IRS mileage rate
The IRS business rate also covers depreciation, insurance and maintenance, not only gas. Mileage reimbursement calculator
Business rate for Jul 1 to Dec 31, 2026: 76¢ per mile. Source: irs.gov.
Turn this trip into an expense report
First report free: log trips with real expenses and export a PDF or Excel report.
How gas cost is calculated
- 1Miles300 miOne way. Round trip = double.
- 2÷ MPG12 gal300 ÷ 25 MPG
- 3× Price$42.0012 gal × $3.50 per gallon
- 4÷ People$14.00Example: split 3 ways
Gas cost by miles and MPG
| Miles | 20 MPG | 25 MPG | 30 MPG | 40 MPG |
|---|---|---|---|---|
| 100 mi | $17.50 | $14.00 | $11.67 | $8.75 |
| 250 mi | $43.75 | $35.00 | $29.17 | $21.88 |
| 500 mi | $87.50 | $70.00 | $58.33 | $43.75 |
| 1,000 mi | $175.00 | $140.00 | $116.67 | $87.50 |
Example price of $3.50 per gallon, not a current price. Miles ÷ MPG × price. Your local price will differ.
Gas cost is not the whole cost of driving
The IRS standard mileage rate covers gas, depreciation, insurance and maintenance, so reimbursement is usually higher than gas alone. Tolls and parking are separate.
Compare: mileage reimbursement calculator. Also see the mileage log generator, rental car calculator and the business trip cost calculator.
Gas cost FAQ
How do I calculate gas cost for a trip?
Divide the miles by your car's miles per gallon to get gallons, then multiply by the price per gallon. Example: 300 miles at 25 MPG is 12 gallons, and at $3.50 per gallon that costs $42.00. Use your own MPG and the price you pay near you.
How much gas do I need for 500 miles?
Gallons = 500 ÷ MPG. At 25 MPG that is 20 gallons; at 30 MPG about 16.7 gallons; at 20 MPG 25 gallons. At an example price of $3.50 per gallon, 500 miles at 25 MPG costs $70.00.
How do I calculate gas for a round trip?
Double the one-way distance, then use the same formula. A 300-mile one-way trip is 600 miles round trip, so it uses twice the fuel and costs twice as much. In the calculator, switch from One way to Round trip.
How do I split gas costs with friends?
Divide the total gas cost by the number of people in the car, including the driver if the driver is chipping in. Example: $42.00 split 3 ways is $14.00 each. Enter the number of people in the calculator to see the per-person cost.
Is gas cost the same as mileage reimbursement?
No. The IRS standard mileage rate is a per-mile amount that covers gas plus depreciation, insurance and maintenance, so it is usually more than gas alone. The calculator shows both side by side for your miles. See the mileage reimbursement calculator for the rate by date.
How do I calculate gas cost in km and litres?
Litres used = km × (L/100 km) ÷ 100. Multiply by the price per litre. To convert, 1 mile = 1.609344 km, 1 US gallon = 3.785411784 litres, and L/100 km = 235.214583 ÷ MPG. Switch the calculator to Km and it converts your numbers for you.
Prices in this page are examples. This is not tax advice; check your employer policy and the IRS page for your situation. Easy Trip Expenses is not affiliated with the IRS.