Fuel Cost Calculator
Free fuel cost calculator. Calculate gas costs for road trips, daily commutes. Split fuel costs among passengers.
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Last updated: January 2026
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Frequently Asked Questions
How do I calculate fuel cost for a trip?
Fuel cost = (Distance ÷ MPG) × Price per gallon. For a 300-mile trip with 25 MPG car and $3.50/gallon gas: (300 ÷ 25) × $3.50 = $42. For round trips, double the distance. In metric: (Distance × L/100km ÷ 100) × Price per liter.
What factors affect fuel efficiency?
Key factors: Speed (optimal is 45-65 mph; above 65 mpg drops significantly), Tire pressure (underinflated tires reduce mpg by 3%), AC use (can reduce mpg by 5-25%), Cargo weight (every 100 lbs reduces mpg by 1-2%), Driving style (aggressive driving uses 15-30% more fuel).
How do I convert between MPG and L/100km?
MPG to L/100km: divide 235.21 by MPG. L/100km to MPG: divide 235.21 by L/100km. Examples: 30 MPG = 7.84 L/100km. 8 L/100km = 29.4 MPG. Lower L/100km is more efficient (opposite of MPG). Most efficient cars: 4-5 L/100km (47-59 MPG).
Is it worth driving farther to find cheaper gas?
Usually no. If gas is $0.10/gallon cheaper 10 miles away and you have a 25 MPG car, you'd use about 0.8 gallons ($2.80) to save maybe $1.50 on a 15-gallon fill-up—a net loss. Only worth it if you're passing by anyway or the savings are significant (>$0.20/gallon).
How much does idling cost?
Idling uses 0.5-1 gallon per hour depending on engine size—$1.75-$3.50/hour. Turn off your engine if stopped for more than 30 seconds (restarting uses less fuel than 30 seconds of idling). Drive-throughs, long traffic lights, and warming up the car all waste fuel.