Maps are used to represent a larger area in a scaled-down format so people can get a birds' eye view of the area. The map scale shows how the distance on the map compares to the distance in real life. The scale will depend on the size of the area being show on the map. For example, an inch may represent a mile on a local map but on a national map an inch may represent 300 miles.
Determine the scale of the map. The scale may be listed as a bar, which shows the distance on the paper on one side and the distance it represents on the map on the other, or as a ratio, such as 1:X. When a ratio is listed without units, it means that one inch on the map represents X inches in real life. For example, a scale of 1:126,720, would mean that each inch on the map represented 126,720 inches, or two miles, in real life.
Measure the distance on the map. For example, if you want to know how many miles it is from City A to Town B, you would measure the distance on the map with a ruler.
Multiply the distance measured on the map by the scale factor. For example, if the distance is 2.5 inches and the scale is 1:126,720, the distance in real life would be 316,800 inches, or 5 miles.
If you are attempting to measure the driving distance between two places, take into account that the road most likely is not perfectly straight. Use a piece of string to trace the road and then measure the length of the string to find a more accurate driving distance.
The larger the area shown by the map, the more distorted the area will be because the earth is round and the map is flat.