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Watch this video to learn about acute, obtuse, right and reflex angles.

An angle is the space between two lines that start at the same point and you measure them in degrees.

Angles can be between 0° and 360°.

A right angle looks like the corner of a square or the edge of a book.

It is a perfect 90°, which is often shown by a small square drawn in between the two lines.

An acute angle is an angles that is less than 90°. This makes them smaller than a right angle.

An obtuse angle is an angle that is bigger than 90° degrees, but doesn’t reach a straight line at 180°.

A reflex angle is an angle that is greater than 180°.

You can measure an angle using a protractor. Let's look at how you do this…

Step 1: Line up the vertex (corner) of the angle with the cross section of the protractor.

Step 2: Make sure that one of the angle lines goes right through the zero.

Remember

These steps are really important - if the protractor isn’t lined up properly with the angle, you won’t get a correct reading.

Step 3: See which number the other line of the angle reaches on the protractor.

Step 4: Take your measurement.

The line goes through both 120° and 60°. Always read from the zero. Since the zero is on the inside line, you continue to read the inside numbers - the angle must be 60°.

You can also tell that the angle is an acute angle so it has to be less than 90°.

Use the protractor to measure this angle. The protractor has already been lined up correctly.

Look for the zero line that the angle line goes through. It is on the inside so you have to read the inside numbers.

The other angle line is in directly between two numbers - 130° and 140°.

The angle measures 135°.

Always check which two numbers the angle is in between and remember the direction the numbers are going in.

It is easy to make a mistake and write 145° instead.

Use the protractor to measure this angle. The protractor has already been lined up correctly.

The zero line is on the left this time, so you need to read the outside numbers.

The other angle line goes directly through 70° and 110°.

The angle must be 70° degrees since it is the outside number.

Label the angles

Can you identify and label the angles correctly in this KS2 Maths interactive activity?

Angle Hunt

Angles are everywhere! Armed with your knowledge of acute , obtuse, reflex and right angles, go on a hunt around your house, garden or even whilst out on a walk and see what angles you can see.

Can you spot at least five examples of each type of angle?

You may wish to record you findings in a table like the one below or take a photo.

Extension challenge

Have a go at measuring some of the angles you find with a protractor!