What is an angle?

An angle is a measure of how much something has turned.

The size of an angle is measured in degrees (°). Angles can be between 0° and 360°:

You can use a protractor to measure the size of an angle.

Activity: Understanding angles

Complete this interactive activity to understand angles. Then put your knowledge to the test.

An angle is created when two lines meet.

There are different types of angles based on their measurement.

Let's look at the different types.

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Right angle
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
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Acute
An acute angle is an angles that is less than 90°. This makes them smaller than a right angle.
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Obtuse
An obtuse angle is an angle that is bigger than 90° degrees, but doesn’t reach a straight line at 180°.
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Straight line
A straight line is 180˚
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Reflex
A reflex angle is an angle that is greater than 180°.

You can use a protractor to measure and draw angles.

A protractor has a clockwise and an anti-clockwise scale. This is so that you can measure angles to the left or right.

Let's have a go at using a protractor to measure some angles.

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What could this angle be? It's a good idea to estimate the angle first and then measure it. You can see it's an acute angle, so it's less than 90°.
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Find the base line on the protractor (it's marked 0° at one end and 180° at the other end). Place the middle of the base line exactly at the point of the angle. Make sure that one of the angle lines goes through the zero.
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Look to see where the other line meets the scale around the edge of the protractor. Here the inner scale shows the size of the angle. This angle measures 65°.
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Let's look at another. Look at this angle. Can you see that this time it's an obtuse angle?
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Look for the zero line that the base angle goes through. It's on the inside, so you must read the inside numbers. The other angle line is between 130° and 140°. So the angle 135°.