Use your road map to calculate mileage by using the distance-scale key on the map. Every road map is different, but each features a key that shows how much space to measure to calculate road miles. Use a ruler or other object to measure the mileage line on the key, and place it on the map repeatedly until you reach your destination. Multiply the number of times you used your ruler to measure the key distance by the number of miles the key represents to figure out the mileage. Other road maps feature the mileage between cities, big and small, which are clearly marked with arrows or colored numbers, and some maps feature mileage charts or grids stating the distance between many major cities, which you can use to calculate your mileage by cross-referencing the number of miles between major cities you're traveling to and from on your trip.
Use an online road map, such as Rand McNally or MapQuest, to calculate your road mileage. Visit either website, and choose the option to calculate your mileage.
Enter your starting location address and your destination location address, and calculate your mileage by clicking on the "calculate" button. View the total miles between your two cities when it appears on the screen. MapQuest even provides a highlighted road map with the directions to your destination when you calculate your mileage.
