Maps are small drawings that explain large areas. In order to make sense of a map, all of the items pictured must be proportional to the real-life counterparts. This means that if there are 20 miles between one building and another, the map of this area must represent a proportionate distance between those items. Since all maps are made with a different purpose in mind, this proportion (ratio) may change from one map to the next. Check the "map scale" to be sure what ratio is being used. The scale of a map may be in the form of a statement, graphic line or numeric equation and can usually be found in the corner of a map.
If the scale says "1 inch = 1 mile," you know that every inch on the map represents one mile in actual distance on Earth. One-to-one is a small scale, perfect for street maps where you don't have to show a large area. Larger scales are used to show states, countries, continents or whenever you have to fit a lot of information onto one page.
If you are making a map, the scale must be precise and reproducible. Be consistent, if you begin with a ratio of 1 inch to 1 mile continue with that scale, or adjust the entire map accordingly. Don't try to approximate distances, use a ruler on paper and an appropriate measuring device when taking full-scale measurements.
