MPG Calculator
Calculate your actual fuel economy from your last fill-up.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the MPG Calculator
The most accurate way to measure your fuel economy is to calculate it from an actual fill-up, not the dashboard estimate. Here is the proper method.
- Fill your tank completely. At your next fill-up, fill the tank to the brim and reset your trip odometer to zero. Do not estimate.
- Drive normally. Run the tank down as you normally would, then fill up completely again at the same type of pump (full service or self-serve, same brand).
- Enter the miles. Read your trip odometer at the second fill-up. That is the miles driven on this calculation.
- Enter the gallons. This is the number of gallons it took to refill at the second stop. This directly measures what was consumed.
- Add gas price (optional). If you want to see cost per mile and total fuel cost, enter the price per gallon at the second fill-up.
About the MPG Calculator
MPG equals miles divided by gallons. L/100km is the metric equivalent: 235.215 divided by MPG. The two scales move in opposite directions. A lower L/100km number is better. Converting between them: a car getting 30 MPG uses 7.84 L/100km. A typical new passenger car averages 28-32 MPG combined. SUVs and trucks typically average 18-26 MPG. Hybrids range from 40-60 MPG. Plug-in hybrids in electric mode are often measured in MPGe (miles per gallon equivalent).
Frequently Asked Questions
Why is my actual MPG lower than the EPA estimate?
EPA fuel economy ratings use standardized test cycles that do not perfectly replicate real-world driving. Common reasons actual MPG falls short: aggressive acceleration and braking, driving at speeds above 65 mph (where aerodynamic drag rises significantly), idling in traffic, cold weather (cold engines and winter-blend fuel reduce MPG 10-20%), cargo weight, roof racks, and incorrect tire pressure. Highway driving at steady speeds often matches or beats EPA ratings.
How do I improve my fuel economy?
The biggest improvements come from: driving at 55-65 mph instead of 75+ mph (each 5 mph above 60 reduces MPG by 5-7%), avoiding jackrabbit starts and hard braking, keeping tires inflated to the recommended pressure, removing unnecessary weight and roof carriers, and using cruise control on highways. Regular maintenance (clean air filter, fresh spark plugs, clean fuel injectors) also maintains peak efficiency.
What is the difference between city and highway MPG?
City driving involves frequent stops and starts, which waste kinetic energy as heat in the brakes and require energy to accelerate again. This typically produces 25-40% lower MPG than highway driving. Hybrids recapture some braking energy (regenerative braking), which is why they show a much smaller gap between city and highway ratings than conventional vehicles.
How many gallons of gas per mile is my car using?
Gallons per mile equals 1 divided by MPG. A car getting 25 MPG uses 0.04 gallons per mile. A car getting 15 MPG uses 0.067 gallons per mile. At $3.50/gallon, the 25 MPG car costs $0.14/mile and the 15 MPG car costs $0.23/mile. The difference seems small per mile but adds up: over 15,000 miles per year, the more efficient car saves $1,350 in fuel annually.