Visit a travel website with maps or a website designed specifically for the purpose of calculating drive times, travel distance and fuel consumption.
Enter your departure city and destination city.
Click on "Calculate" to see the distance and the recommended route for your travel.
Use the distance equation to calculate mileage if you have access to the other variables, distance and rate.
Find the rate, which is the speed you travel. If you are traveling on highways, you might average 55 or 60 mph; if you have to go through towns on your way to the destination city, it might take your average rate of speed down to 45 or 50 mph.
Keep track of the time it takes you to travel between cities. You can look for an average on a website or a map, if you do not remember the exact time it took you between the two cities.
Multiply the rate of speed by the time it takes you to travel and the result will be the distance traveled.