MPG Calculator
Enter your odometer readings and how much fuel you added at the refill — your real mpg updates as you type, and the link in your address bar always reflects your numbers.
How this calculator works
This is the classic "fill to full" method, done for you: subtract your starting odometer reading from your ending reading to get the miles you actually drove on that tank, then divide those miles by the gallons it took to refill — miles = endOdometer − startOdometer, mpg = miles ÷ gallons. If you enter a gas price, we also divide it by your mpg to show a cost-per-mile figure, handy for comparing trip costs or commute expenses at a glance.
Worked example
Odometer reads 45,000 at a fill-up, and 45,350 at the next one, taking 12.5 gallons to refill: that's 350 miles driven, so 350 ÷ 12.5 = 28.0 mpg. At $3.50 a gallon, that works out to $3.50 ÷ 28 = $0.125 per mile — about 12.5 cents for every mile you drive.
Frequently asked questions
Why calculate my own mpg instead of trusting the window sticker?
The EPA rating on the window sticker comes from a standardized lab test cycle, useful for comparing vehicles but not a promise of what you'll actually get. Your real-world mpg depends on your driving style, the terrain you cover, traffic, load, and weather — measuring it yourself from an actual fill-up tells you what your car really does, in your hands, on your roads.
How accurate is the "fill to full" method?
It's the standard way to measure mpg without a trip computer, and it's reasonably accurate over a full tank: fill the tank completely, zero your trip odometer (or just note the reading), drive normally, then refill to full again and record the gallons it took. Over a full tank the small variances in pump shut-off average out; over a partial fill they matter more, so full-tank-to-full-tank readings are the most trustworthy.
Does short-trip driving affect mpg?
Yes. A cold engine burns more fuel until it reaches operating temperature, so a string of short trips typically shows noticeably lower mpg than the same distance covered in one longer highway drive. If your measured mpg looks worse than expected, your mix of short local trips versus longer drives is a common reason why.
What's a good mpg?
It depends heavily on the vehicle class you're comparing against. Compact and midsize sedans commonly reach 30+ mpg combined, hybrids often do meaningfully better, while trucks, larger SUVs, and vehicles towing cargo typically land lower — sometimes in the high teens to low 20s. There's no single "good" number that applies across every vehicle type.