Choosing the measuring unit

When measuring length, weight or capacity you have to decide which is the most suitable measuring unit to use.

Here's a reminder of the different metric units you can use:

When choosing the suitable unit for measuring you need to consider:

• What it is you are measuring - for example is it long or short, heavy or light?
• You can then estimate how big it is.
• What unit will give you the smallest number of whole digits?
• For example it is easier to write 4 m rather than 4 000  mm.

Here's an example. What unit would you use for measuring the length of a swimming pool? Lets go through the points:

• A swimming pool is quite long and is always referred to in metres. A standard pool can be 25 m long and an Olympic size pool is 100 m long.
• It's best not to give the length of a pool in cm or mm because the units would be very long.
• A 25 m pool would measure 25 000 mm or 2 500 cm.
• At the other end of the scale, you would not refer to the length of a pool in kilometres either. A 25 m pool would be 0.025 km.

In mm it would be 25 000 mm

In cm it would be 2 500 cm

In m it would be 25 metres

In km it would be 0.025 km