Hold up your pencil and take a good look at it. Roughly how long is it? Have a guess in your head before anyone says a number out loud.

Now look at the little dot of glue on a glue stick, or the rubber on the end of a pencil. Would you measure those tiny things in the same way as you would measure the whole desk?

We will measure four real objects with the ruler at the front. Each time, estimate first, then measure. Watch closely where the ruler lines up at each end, and notice that some lengths land between the centimetre marks.

Now it is your turn at your own desk. Take out your ruler. I will name an object on your desk, and you will measure it to the nearest millimetre.

Time for a measuring challenge at your desk. Estimate each one first, then measure it to the nearest millimetre and record both: your pencil, your rubber, the edge of your copybook, your ruler's width, and your handspan.

Stretch: when you have finished the five, can you find something on your desk that is exactly 7 cm long?

What we did today

• We estimated a length first, then measured it.
• We lined the zero up with one end and read the far end to the nearest millimetre.
• We chose centimetres and millimetres for small everyday lengths.

Coming up

Next we will measure longer things and decide when to use metres instead of centimetres. We will measure the door, the whiteboard and even the corridor, and choose the sensible unit each time.