Fuel Cost Calculator

1. Choose your unit system. US drivers typically use MPG (miles per gallon). Most other countries use L/100km (liters per 100 kilometers).
2. Enter your trip distance. This is the one-way distance of the trip you want to estimate.
3. Enter your fuel efficiency. Find your vehicle's MPG rating on the window sticker, your owner's manual, or fueleconomy.gov. For a more accurate estimate, track your own fuel usage over several fill-ups.
4. Enter the current gas price. Check GasBuddy.com or Google for local gas prices, or use the AAA national average.
5. Enter monthly and annual mileage to see projected fuel costs over time. The US average is about 15,000 miles per year.

The fuel cost formula for MPG systems:

Fuel needed (gallons) = Distance (miles) / MPG
Trip cost = Fuel needed × Gas price ($/gallon)
Cost per mile = Gas price / MPG

Example: 300-mile trip in a car getting 30 MPG with gas at $3.50/gallon:

Fuel needed = 300 / 30 = 10 gallons
Trip cost   = 10 × $3.50 = $35.00
Cost/mile   = $3.50 / 30 = $0.117/mile

For L/100km:

Fuel needed (liters) = Distance (km) / 100 × L/100km
Trip cost = Fuel needed × Price per liter

Annual cost formula:

Annual cost = (Annual miles / MPG) × Gas price

Going from 25 MPG to 35 MPG saves $300/year at $3.50/gallon and 15,000 miles. That adds up to $1,500 over 5 years, which is relevant when comparing vehicle purchases.