Read the scale on the map. If it is a bar, it will appear with a length on the map (usually about 1 or 1/2 inch), or if it is a ratio, it will state a distance. Next to or over the bar or on the other side of the ratio, it will describe a number of miles, kilometers or another distance of measurement. For example, a 1-inch bar marked as "15 miles" or the ratio 1-inch:15-miles means that every inch of the map represents 15 miles.
Use the ruler to measure a 1-inch or 1/2-inch (or whatever the scale of your map says) section of road on the map. This section represents the distance on the scale. Following the example, that 1-inch section of the map represents a 15-mile stretch of road.
Measure the distance between two points on the map. For example, the distance between two towns on a highway. If the two appear 3 1/2 inches apart on the map, this means they are 52 1/2 miles apart in the real world. Repeat this measurement for any other distances you need to measure.
Locate a point you have driven past recently, if you are driving in a car and reading the map. Measure the distance from that point to your destination, and multiply it using the ratio. For example, if you passed a town 2 inches away from your destination on the map, and the scale is 1 inch:15 miles, then you have 30 miles to go.
