Locate the map key. The map key looks like a tiny ruler, and it's usually located in one of the four corners of a map. The map key tells you how many inches or centimeters on the map equals a specific number of miles or kilometers. For example, one inch might equal 20 miles.
Locate your starting and ending points on the map.
Place one end of the ruler at the location you are leaving from and the other end at your destination location. Depending on how far you are traveling you may need to move the ruler several times. If so, keep track of the number of times you moved the ruler.
Multiply the inches between the two locations by the distance information on the map key. For example, if one inch equals 20 miles and you are traveling four inches as measured by the ruler, multiply 20 by 4 to get a travel distance of 80 miles.
