Large Scale and Small Scale Maps

I’ve noticed that the topic of large scale and small scale maps gets overcomplicated a lot.

It’s actually easy to understand once you realize where the terms come from. The part that makes it a bit confusing is that it’s opposite of what you might initially think.

When I think of large scale maps, without having the knowledge I do on the topic, I would assume that large scale maps show a large area. So, for example, a map showing the entire United States would be a large scale map and a map showing a neighborhood in a city would be a small scale map, but this is wrong!

Now, to understand why it’s wrong.

The terms large scale and small scale are used to describe the scale of a map. For an example, let’s analyze the ratio 1 to 50, which can be written as either 1/50 or 1:50. A map scale of 1/50 means that 1 unit on the map is equal to 50 units on earth’s surface. So, 1 inch on the map is equal to 50 inches on the ground and 1 foot on the map is equal to 50 feet on the ground. Another way to think about it is that 1 unit on the map is 1/50th its size on the earth’s surface.

Now, to really understand what’s going on, let’s compare the map scale of 1/3 with that of 1/300,000. So pull out your calculator and figure out what these fractions equal in decimal format.

1/3 = 0.333333 repeating (larger, closer to earth)

1/300,000 = 0.00000333333 repeating (smaller, further from earth)

As you can see, the map scale of 1/300,000 is A LOT small than that of 1/3, and this is where the terms small scale and large scale come from. So, this means, the further away from earth we get, the smaller the fraction becomes and the closer to earth we get the larger the fraction becomes.

Depending on the map scale someone commonly works with, their idea of what is considered small scale or large scale might differ from someone else. For example, if someone normally works with maps at a scale of 1:1,500, they might consider 1:25,000 a small scale map while another person who normally works with maps at a scale of 1:1,000,000 might consider 1:20,000,000 a small scale map. Obviously, these two terms mean different things to different people and there’s no standard, so everyone is correct!

A very common map scale used by engineers and other professions is 1:63,360 because this correlates to 1 inch on the map being equal to 63,360 inches on the ground. This can otherwise be described as 1 inch on the map is equal to 1 mile on the ground because there are 63,360 inches in one mile. So, if you see this map scale used often, that’s why.

Hopefully, this gave a better understanding of large scale and small scale maps.