About Fuel Economy Calculator

Three calculators in one: compute MPG from miles driven and gallons used, estimate annual fuel costs from a known MPG, or price out a specific trip. Each mode shows cost breakdowns and the MPG mode rates your vehicle’s efficiency on a six-tier scale from Excellent (40+ MPG) to Poor (<15 MPG). CO₂ emissions are estimated at 19.6 pounds per gallon of gasoline. A calculation history (up to 10 entries) can be exported as CSV.

• MPG mode: miles ÷ gallons with efficiency rating and annual cost projection
• Cost mode: annual fuel spend and cost-per-mile from known MPG and fuel price
• Trip mode: gallons needed and total fuel cost for a given distance
• CO₂ calculated at 19.6 lbs/gallon × annual gallons consumed
• Efficiency comparison grid benchmarks your car against 15, 25, 35, and 50 MPG vehicles

Frequently Asked Questions

Where does the 19.6 lbs per gallon CO₂ figure come from?

The EPA’s standard emission factor for gasoline combustion. Diesel is higher (~22.4 lbs). This tool assumes gasoline only.

How do I convert between MPG and L/100km?

The tool handles both directions automatically. Enter your distance and fuel consumed in either imperial or metric units, and it shows the result in both MPG (US) and L/100km. The conversion factor is 235.215 divided by the MPG value.