In geography, a linear scale is a bar or line graphic that shows the distance on the map that is equal to a real-world distance, such as 100 miles. Linear scales are also called bar scales or graphical scales.
Linear scales have a distinct advantage over other map scales because they are printed on the map, and the proportions stay the same if the map is enlarged or reduced during reproduction. To use a linear scale, measure the distance on the map that you want to convert. Then, place the measuring stick on the linear scale, and use the provided information to convert the map distance to a real-world distance.