MPG Calculator
Calculate your vehicle's miles per gallon (MPG) from the miles driven and gallons used at your last fill-up.
What is MPG Calculator?
The MPG calculator tells you how many miles your car gets per gallon of gas — the standard fuel-economy measurement in the United States. It is the single best number for comparing cars, tracking driving habits, and budgeting for fuel.
Enter the miles you drove since your last fill-up and the gallons it took to top off and the calculator returns real-world MPG, cost per mile, and projected annual fuel spend.
Formula
MPG = miles driven ÷ gallons used
Cost per mile = (gallons × $/gallon) ÷ miles. Annual fuel cost = annual miles × cost per mile.
Gallons per 100 miles (GPM) = 100 ÷ MPG — useful because GPM scales linearly with fuel use while MPG does not.
Worked example
You drive 320 miles, fill up with 11 gallons at $3.45/gal:
- MPG = 320 / 11 ≈ 29.1
- Cost per mile = (11 × 3.45) / 320 ≈ $0.119
- For 13,500 miles/year, fuel cost ≈ $1,603
How to use this calculator
- Fill your tank completely and reset the trip odometer.
- When you next fill up to full, record the trip miles and the gallons from the pump.
- Enter those two numbers here. Do it for 2–3 tanks and average for a more reliable result — one tank can be skewed by short city drives or long highway trips.
- Enter your local gas price and annual mileage to see your projected fuel cost.
Frequently asked questions
Why does my MPG differ from the EPA sticker number?
EPA ratings are measured in a lab using standardized cycles. Real-world MPG depends heavily on your speed, climate, tire pressure, vehicle load, driving style, and terrain. Most drivers get 5–20% less than the sticker. fueleconomy.gov shows actual owner-reported ranges.
How can I improve my gas mileage?
The biggest wins: slow down from 80 mph to 65 mph (saves 15–20%), avoid jackrabbit starts and hard braking, remove roof racks when unused, keep tires inflated to the door-jamb spec, and combine short trips since cold engines use much more gas for the first few minutes.
Should I use premium gas if my car is rated "regular"?
No. Premium gas in a regular-spec engine gives no MPG benefit — you are just paying more. Use the grade your owner's manual specifies.
Why is "gallons per 100 miles" more useful than MPG?
MPG is non-linear. Going from 10 → 20 MPG saves twice as much fuel as 30 → 40 MPG for the same miles driven. GPM (gallons per 100 miles) is linear and easier to compare across vehicles.