Measuring Length

We use rulers to measure small lengths

Rulers use centimetres and millimetres

You can use millimetres to measure the length, width, height, or thickness of small objects.

A dime is about 1 mm thick.

This pine needle is about 6 cm long.

To be more precise, you read the length in millimetres.

The pine needle is 62 mm long.

One millimetre is one-tenth of a centimetre.

The pine needle is 6.2 cm long.

So, you can also read the length of the pine needle in centimetres.

You say: 6 and 2 tenths centimetres

We use referents to quickly estimate length

Your little finger is a good referent for a centimetre (cm)

The width of your door is a good referent for a metre (m)

You need to multiply or divide when you are converting between different metric units

The picture on the right is very clear