Gas Mileage Calculator
Calculate your car's fuel economy (MPG) and cost per mile.
How do you calculate gas mileage (MPG)?
Miles per gallon (MPG) is calculated by dividing the number of miles you drove by the number of gallons of gasoline your car used to cover that distance. For example, if you drive 300 miles and use 10 gallons of gas, your car is getting 30 MPG. Tracking your MPG over time, especially across different seasons and driving conditions, gives you a realistic picture of your vehicle's real-world fuel economy — which is often different from the EPA-estimated MPG on the window sticker.
Why does my actual MPG differ from the sticker rating?
EPA fuel economy ratings are measured under controlled lab conditions, but real-world MPG is affected by driving style, terrain, tire pressure, vehicle load, outside temperature, and how much city versus highway driving you do. Aggressive acceleration and heavy braking can lower MPG by 10-30%, while cold weather increases engine warm-up time and can reduce winter fuel economy by 15-20% compared to summer driving.
How does MPG affect your cost per mile?
Your cost per mile is simply the price of gas divided by your MPG — the higher your MPG, the lower your cost per mile driven. This calculator uses your actual MPG and local gas price to estimate exactly what a 100-mile trip costs you, which is useful for budgeting road trips, comparing vehicles before you buy, or deciding whether it's worth driving to a cheaper gas station further away.
Frequently Asked Questions
How do I calculate my car's gas mileage?
Fill up your tank completely, reset your trip odometer, drive normally until you need to fill up again, then divide the miles driven by the gallons it took to refill the tank. That figure is your real-world MPG for that tank of gas.
What is considered good gas mileage?
For a standard gasoline sedan, 30-40 MPG is considered good, while SUVs and trucks typically average 18-25 MPG. Hybrid vehicles often achieve 45-60 MPG, and the specific number that's "good" depends heavily on the vehicle class you're comparing.
Why does my gas mileage change between fill-ups?
MPG naturally fluctuates based on driving conditions — more city stop-and-go traffic, cold weather, carrying heavy loads, using air conditioning, and aggressive driving all reduce fuel economy compared to steady highway cruising in mild weather.
How can I improve my car's gas mileage?
Keep tires properly inflated, avoid rapid acceleration and hard braking, remove excess weight from the vehicle, use cruise control on highways, and keep up with regular maintenance like air filter changes and oil changes — these steps can collectively improve MPG by 10% or more.
How do I calculate cost per mile from my gas mileage?
Divide the price you pay per gallon of gas by your car's MPG. For example, at $3.50 per gallon and 30 MPG, your cost per mile is about $0.12, which you can then multiply by any trip distance to estimate fuel costs.
Why is my actual MPG lower than the EPA-rated MPG on the window sticker?
EPA ratings are generated under standardized lab conditions that don't fully capture real-world variables like traffic, weather, terrain, and individual driving habits, so most drivers see MPG that's somewhat lower than the sticker estimate, especially in city driving.
Does the type of gas I use affect my mileage?
For most vehicles designed to run on regular unleaded, using premium gas provides no mileage benefit. However, vehicles that require premium fuel may experience reduced performance and slightly lower MPG if you use regular gas instead, since the engine's timing may adjust to prevent knocking.
How much gas will I use on a 100-mile trip?
Divide 100 by your car's MPG to get the gallons needed, then multiply by your local gas price for the cost. At 30 MPG, a 100-mile trip uses about 3.3 gallons — roughly $11.67 at $3.50 per gallon.