5-cent Map of Bequia Island watermarked stamp
The ‘3 Nautical Miles’ graphic scale at bottom left is an excellent example of its use.
2-cent Map of British Empire on Mercator Map stamp
Using the grid network, this world map on Mercator projection is determined to be on the scale of 1:1,250,000,000 at the equator. That means that .1 of an inch on the stamp equals 1,973 miles on earth.

Every map is smaller than the portion of the earth it represents. Scale is the proportion of the map to the actual area shown on it; e.g. 1/2-inch (on the map) equals 50 miles. It states the area and distance relationships if measurements are necessary.

Scale is shown by a line segment divided into certain units of lengths (a graphic scale). The presence of a scale allows the user to determine the extent of the mapped area. When scale is expressed as a ratio (with the first term always being 1), it is called a representative fraction. This ratio was first used in France in 1806 and was quickly adopted as a sort of ‘international language’.

Since all maps distort – and the distortion might vary from one part of the map to another – a scale will give only an approximation. But on larger scale maps, which include only a small portion of the earth, the distortion may be negligible and the scale more accurate.