A beginners guide to understanding map scales

National Map Reading Week

Have you ever got confused about what a map scale is, or wondered what is the difference between our Landranger and Explorer maps? Our quick guide to understanding map scales will help!

Choosing the right map scale can be really important when you are planning you adventures. Use a map with too little detail and it can be hard to use, while too detailed a map may mean you are continually going off the page or map sheet.

The critical item that tells you how much detail is shown is called the 'scale'.

What is a map scale?

The scale of a map shows how much you would have to enlarge your map to get the actual size of the piece of land you are looking at. For example, your map has a scale of 1:25 000, which means that every 1cm on the map represents 25 000 of those same units of measurement on the ground (for example, 25 000cm = 250 metres). That might sound a bit complicated, but OS maps have been designed to make understanding scale easy. Look at the front of a 1:25 000 scale map and you will see that the scale has been also written out for you like this:

4cm to 1km

This means that every 4cm on a map = 1km in real life. To make it even easier, the grid lines are exactly 4cm apart, so every square is 1km by 1km.

Maps are made at different scales for different purposes. The 1:25 000 scale map is very useful for walking, but if you use it in a car you will quickly drive off the edge! On the other hand, maps at 1:250 000 scale (note the extra zero) show lots more area, but in far less detail.

A map scale is the size ratio of a feature on the map to the one in the real world

Popular OS map scales

Road maps: 1: 250 000 scale, shows roads and towns, but few individual features over a large area

Landranger maps: 1 : 50 000 scale, shows roads, large paths and some individual features

Explorer Map: 1 : 25 000 scale, shows many features including paths and buildings over a small area

Mastermap: 1: 1 250 scale, shows accurate position for individual buildings or small areas

Example of 1: 250 000 scale mapping

Example of 1: 250 000 scale mapping, showing roads but few other features and ideal for driving

Example of 1: 50 000 scale mapping

Example of 1: 50 000 scale mapping with road and some other features for cycling and holidays

Example of 1: 25 000 scale mapping

Example of 1: 25 000 scale mapping shows most paths and individual buildings with enough details for walking and MTB

Example of 1: 1250 scale mapping

Example of 1: 1250 scale mapping showing a small area, normally used for building and construction

Steve Backshall on map scales

Large Scale vs Small Scale

The terms 'large scale' and 'small scale' are used to describe different scales. However, they can be confusing :

Large scale maps have low number is the scale, such as 1: 1250. The features are shown are large
Small scale maps have a high number in the scale, such as 1: 250 000. Individual features shown are small

High number = small scale

There is no fixed definition of what scale ratios fall into large scale or small scale.

More reading: Advanced guide to map scales

This is part of National Map Reading Week, which encourages everyone to improve their map reading skills and discover new adventures.

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