The term "scale" refers to the relationship between distance on the map and distance on the ground. Generally, it is given as a fraction or ratio, such as 1:100,000 or 1:10,000. The first number represents the map distance, and is always 1. The second number represents the ground distance and is different for each scale.

For example, a scale of 1:10,000 means that one inch on a map corresponds to 10,000 inches on the ground (or one centimeter on the map corresponds to 10,000 centimeters on the ground). On a 1:100,000-scale map, one inch on a map corresponds to 100,000 inches on the ground.

The scale of a map is also related to its detail. A 1:100,000-scale map is usually much less detailed than a 1:10,000-scale map. This is because a one-inch-by-one-inch map square can only hold so much detail. Using a square inch of paper to depict a 100,000-square-inch ground area makes it necessary to omit some details of the terrain. Because of the size (on paper) of terrain features, such maps are known as "small-scale" maps. Generally speaking, small-scale maps cover a large area of land, at low detail.

When depicting a 10,000-square-inch ground area, the cartographer can "fit" more details in the square inch of paper. Such maps are called "large-scale" maps: they cover smaller land area, but at greater detail. The smaller the second scale number (e.g. 10,000), the "larger:  the map scale. The larger the number, the smaller the scale.