Mileage Calculator
Enter the miles you drove and the gallons you used over the same stretch, and the calculator divides one by the other to give your real MPG to one decimal, rated from Poor (under 15 MPG) to Excellent (40 MPG or more). The most reliable inputs come from two full fill ups: the trip meter miles between them and the gallons the second fill takes.
How to Use This Calculator
Fill the tank and zero the trip meter
Fill until the pump clicks off, then reset the trip meter or write down the odometer reading.
Drive, then fill up again
Enter the trip meter miles as Distance Traveled and the gallons on the second receipt as Fuel Used.
Combine several tanks for a steadier average
Add the miles and the gallons before dividing: 300 + 340 miles on 10.5 + 11.5 gallons is 640 ÷ 22 = 29.1 MPG.
Formula and Logic
Divide the miles driven by the gallons used. The calculator rounds the result to one decimal.
MPG = Miles Driven ÷ Gallons UsedBoth numbers must cover the same stretch of driving. If you top up partway, add those gallons to the fill that closes the stretch, or the result will come out too high.
Example Calculations
Example 1: Daily commuting
Inputs
Result
28.6 MPG
320 ÷ 11.2 = 28.6 MPG, which the calculator rates Average (22 to 29.9 MPG).
Example 2: Short city driving
Inputs
Result
25.0 MPG
150 ÷ 6 = 25.0 MPG, also Average. Braking, idling and stop and go traffic usually pull city results below highway ones.
Example 3: Highway road trip
Inputs
Result
35.0 MPG
420 ÷ 12 = 35.0 MPG, rated Good (30 to 39.9 MPG). Steady driving at a consistent speed on open roads often gives results like this.
What a Few MPG Points Are Worth
A 5 MPG difference sounds small until you price it. Driving 1,000 miles a month at 25 MPG burns 40 gallons; at 30 MPG it burns about 33.3. At an example price of $3.80 a gallon, that 6.7 gallon gap is worth about $25 a month, or roughly $300 a year, without driving a single mile less.
That is the practical reason to measure your real MPG every few fill ups. A slow drop from underinflated tires or a maintenance problem shows up in this number before it shows up anywhere else.