Reading a Map Scale: From Centimetres to Kilometres

0:00On this map, a campsite and a lookout are 3.2 centimetres apart. How far apart are they on the ground?

0:08The scale is 1 to 50,000. A scale is a ratio: map length to real length.

0:16So 1 centimetre on the map stands for 50,000 centimetres on the ground.

0:22To find the real length, multiply: 3.2 times 50,000 is 160,000 centimetres.

0:31Stopping here, in centimetres, is a common mistake: 160,000 centimetres is hard to picture.

0:39100 centimetres make 1 metre, so divide by 100 to get 1600 metres.

0:471000 metres make 1 kilometre, so divide by 1000 to get 1.6 kilometres.

0:55Dividing by 1000 moves the decimal point 3 places to the left: 1600 becomes 1.6.

1:05Moving the point only 2 places gives 16 kilometres, which is wrong.

1:11Check: 50,000 centimetres is 500 metres, and 3.2 times 500 metres is 1600 metres.

1:21So the campsite and the lookout are 1.6 kilometres apart on the ground.

1:27A house plan works the same way. At a scale of 1 to 100, this wall is 4.5 centimetres long.

1:354.5 times 100 is 450 centimetres, and 450 divided by 100 is 4.5 metres.

1:46Multiply by the scale, then convert the units: 3.2 centimetres on the map is 1.6 kilometres on the ground.