Draw and measure accurately

How accurate you need to be when you measure depends on the situation.

To measure and draw well, you need to know how to use a ruler and understand the different units of measurement, such as millimetres and centimetres.

Sometimes, you need to be very exact, so you might have to measure to the nearest millimetre.

At other times, it might be better to round up or down to the nearest centimetre.

Complete this interactive activity to understand how to draw and measure accurately. Then put your knowledge to the test.

When measuring length you can use centimetres (cm) and millimetres (mm).

Take a look at this ruler. You can see there are ten millimetres in one centimetre (cm).

To measure something to the nearest centimetre, you look at the centimetre closest to the end of the object you are measuring.

In this next picture, look at the end of the pencil with the rubber on it and take a measurement using the ruler below:

The length would be 7cm to the nearest centimetre. You can see it doesn't pass the half way mark, so it is closer to 7cm than to 8cm.

However, you won't always have to round down to the nearest centimetre. Sometimes you will have to round up. It depends on the length of the object.

Take a look at this book and ruler:

The book is 10cm to the nearest centimetre because it is closer to 10cm than to 9cm.

If you need to be really accurate, measure and give your answer in centimetres and millimetres.

Take a look at the piece of wood below. You can find its length by looking closely at the marks for centimetres and millimetres. The arrow shows its exact length is 9cm and 3mm.