Gas Trip Cost Calculator

Fuel is (distance ÷ MPG) × price per gallon. For a 300-mile drive in a car that gets 28 MPG with gas at $3.50, that is 300 / 28 = 10.7 gallons, or about 10.7 × $3.50 = $37.50. Add tolls for the total. Choose round trip to double the distance automatically.

Whatever MPG figure goes into this calculator decides the whole estimate, so where that number comes from is worth a second thought. A trip computer's real-time MPG readout is convenient but imprecise — it is calculated from fuel-injector timing rather than actually measured fuel volume, and it drifts over a tank. The more reliable number comes from measuring at the pump: reset the trip odometer at a fill-up, drive normally, then divide the miles covered by the gallons the next fill-up actually takes. That figure reflects your specific driving, route and conditions, which a window-sticker EPA rating cannot.

MPG and fuel used are inverse, not proportional, and that has a real practical consequence: the gas saved by improving MPG shrinks the higher your MPG already is. Going from 15 to 20 MPG on a 300-mile trip saves 5 gallons (20 down to 15); going from 30 to 35 MPG on the same trip saves only about 1.4 gallons, even though both are "5 MPG improvements." That is why a heavy vehicle's efficiency upgrade often matters more in absolute fuel terms than the same MPG gain on a car that was already efficient — measuring in gallons per 100 miles instead of MPG makes comparisons like this much more intuitive, since that measure is linear.

Group trips are cheaper per person. Enter how many people are splitting to see each share — handy for carpools and splitting fairly, with fuel and tolls in the same pot. It does not include food, lodging or parking, which typically need to be tallied and split separately since they rarely divide as evenly as a fixed per-mile fuel cost.

This estimate covers fuel and tolls — the variable costs of the drive itself. It leaves out wear and tear, depreciation, parking, food and lodging, all real costs of a road trip that simply don't scale with distance the same clean way fuel does. For the full ongoing cost of every mile you drive, including maintenance and insurance folded in, use the cost-per-mile calculator instead — this one is built specifically for a single trip's fuel budget.