Measuring distance on a map using its scale
Geography · Key Stage 2 · The School
What a scale actually says
A map SCALE compares map distance to real distance. A scale of 1:50,000 means one unit on the map equals fifty thousand of the same unit in real life. One centimetre on the map equals five hundred metres on the ground. Every printed map states its scale clearly, usually near the key. Without it, no distance on the map could ever be trusted.
Map to real world
Measure a distance on the map in centimetres. Multiply it by the scale number. That gives the real distance. A four centimetre gap on a 1:50,000 map means two kilometres in real life. The same method works for any scale at all.
Real world to map
This also works the other way round. Take a real distance and divide by the scale number. That tells you how big to draw it on the map. Both directions use exactly the same idea. Getting this backwards is a very common mistake.
A walker wants a route close to five kilometres long. The map scale is 1:25,000. Five kilometres is five thousand metres. Divide that by 25,000. The answer is 0.2, in the same units as the map. That means the route needs to measure twenty centimetres on the map. The walker measures a route with a piece of string. They adjust it until the string is exactly twenty centimetres long. That route, followed on the ground, will be almost exactly five kilometres. The same trick works for any distance, on any scale of map.