Fuel Economy Calculator
Optional — enter to calculate cost per mile/km
Enter Your Vehicle Data
Select a calculation mode, fill in your fuel and distance details, and see your fuel economy, costs, and efficiency rating instantly.
How to Use the Fuel Economy Calculator
Choose Your Unit System and Mode
Start by selecting Imperial (MPG, miles) or Metric (L/100km, km) depending on your country and vehicle. Then choose the calculation mode: Fill-Up Tracker to calculate your real-world MPG from odometer readings, Trip Planner to estimate fuel cost for a journey, Annual Cost to project your yearly fuel spending, or Compare Vehicles to see which car is cheaper to operate.
Enter Your Fuel and Distance Data
For Fill-Up Tracker: enter your previous and current odometer readings plus the amount of fuel added. For Trip Planner: enter the trip distance and your vehicle's fuel efficiency. For Annual Cost: enter your annual mileage and optionally toggle on city/highway blend to use separate city and highway efficiency figures. For Vehicle Comparison: enter the efficiency and fuel price for each vehicle plus your annual distance.
Add Optional Cost Information
Enter the current fuel price per gallon or per liter to calculate cost metrics. In Trip Planner and Annual Cost modes this is needed for cost estimates. In Vehicle Comparison mode, you can enter the price difference between vehicles to calculate how many months it takes for the fuel savings to pay back the higher purchase price of the more efficient vehicle.
Review Your Results and Export
Your results show fuel economy in MPG, L/100km, and km/L simultaneously, plus an efficiency rating bar, cost breakdown, and CO2 emission estimate. Use the Export CSV button to save your results for records or budgeting, or the Print button for a printable summary. In Annual Cost mode, the bar chart shows your weekly, monthly, and annual cost in proportion to help visualize your fuel spending.
Frequently Asked Questions
How do I calculate my real MPG accurately?
The most accurate method is the full-tank fill-up approach. Fill your tank completely, note your exact odometer reading, then drive normally until your next fill-up. Fill the tank completely again, record the new odometer reading and the exact amount of fuel added. Divide the miles driven by the gallons used. This averages out variations from short trips, idling, and speed changes. Repeat over several fill-ups and average the results for the most reliable figure. Single-fill-up readings can vary by 10 to 15 percent due to driving conditions on that particular tank. The calculator does this math instantly once you enter the three values.
Why does my actual MPG differ from the EPA estimate?
EPA estimates are conducted under controlled laboratory conditions that do not fully replicate real driving. Tests are run on a dynamometer (not on the road), at controlled temperatures, without air conditioning, and according to standardized speed profiles that differ from typical highway and city driving. Real-world MPG is affected by driving speed (fuel economy drops sharply above 55 to 60 mph), aggressive acceleration and hard braking, air conditioning use (reduces MPG by 5 to 25 percent), cold weather (increases fuel use by 15 to 20 percent), and vehicle load. Most drivers achieve 10 to 20 percent lower than the EPA estimate, which is why measuring your actual fill-up efficiency is more useful for budgeting.
What is a good MPG for a car?
What counts as good fuel economy depends heavily on vehicle type. For compact and mid-size sedans, 30 to 40 MPG is considered good, and hybrids often achieve 50 to 60 MPG. SUVs and crossovers typically range from 22 to 35 MPG. Full-size trucks and large SUVs generally achieve 15 to 25 MPG. Electric vehicles are measured in miles per kilowatt-hour (MPkWh) rather than MPG. As a general benchmark for gasoline vehicles: under 20 MPG is poor, 20 to 27 is below average, 27 to 35 is average, 35 to 45 is very good, and above 45 MPG is excellent. The average fuel economy of new vehicles sold in the United States is approximately 26 MPG.
How is CO2 emission estimated from fuel use?
The CO2 estimate is based on the carbon content of gasoline. When one gallon of gasoline is burned, it produces approximately 8,887 grams (8.887 kg) of carbon dioxide. This figure comes from the US Environmental Protection Agency and is based on the density and carbon content of standard gasoline. For diesel, the figure is approximately 10,180 grams per gallon. This calculator uses the gasoline figure as its default. Your actual CO2 output may vary based on ethanol content in the fuel (E10 fuel with 10 percent ethanol produces slightly less CO2 per gallon) and engine combustion efficiency. These estimates are useful for comparing vehicles and calculating a rough annual carbon footprint from driving.
How does the vehicle comparison payback calculation work?
The payback period shows how many months of fuel savings it takes to recover the higher purchase price of a more efficient vehicle. For example, if Vehicle B costs $3,000 more than Vehicle A but saves you $1,200 per year in fuel, the payback period is 30 months (2.5 years). After that point, Vehicle B is cheaper in total cost of ownership. This is a simplified calculation that does not account for financing costs, insurance differences, depreciation, or maintenance cost differences between vehicles. If the payback period exceeds the typical ownership period of five to seven years, the cheaper vehicle may actually be more economical overall despite worse fuel efficiency.
What is the city/highway blend and why does it matter?
Most vehicles have separate city MPG and highway MPG ratings because driving conditions affect efficiency differently. City driving involves frequent stops and starts, low speeds, and more idling — which wastes fuel. Highway driving at steady moderate speeds is generally more efficient for conventional gasoline engines. The EPA uses a standard blend of approximately 55 percent city and 45 percent highway driving to derive the combined MPG shown on window stickers. Your actual split depends on where you drive. If you commute mostly in urban areas, your real-world efficiency will be closer to the city rating. Use the blend mode in Annual Cost calculations to input your actual city and highway efficiency values along with your personal city/highway driving percentage for a more accurate annual fuel cost estimate.