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Measure Angles using a Protractor

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Videos, examples, solutions, stories and songs to help Grade 4 to Grade 6 students learn how to measure angles in degrees using a protractor.

A degree is the unit used to measure rotation within a circle and can be used to measure angles. The measure of rotation for a full turn within a circle will always be 360°. This is true regardless of the size (diameter) of the circle.

You can construct your own 360° protractor using a circular piece of paper.
• A circle (full turn) has a measure of 360°.
• Fold the circle in half. If a full circle measures 360°, a half of a circle must
measure 180°.
• Fold the half circle in half again. This represents a quarter of the whole circle. If half
of the circle measures 180°, a quarter must measure 90°.
• Fold the quarter circle in half again. This represents an eighth of the whole circle. If a
quarter of the circle measures 90°, an eighth must measure 45°.
• Unfold the circle. There should be eight sets of 45° in the whole.
• Choose a fold line as 0°; label each fold line in the counterclockwise direction as a consecutive multiple of 45°, as shown below.
Construct own Protractor

When measuring angles using a protractor it is important that the reading always begins at zero. Do not make the mistake of beginning at the 180° mark. You must always line up one arm of the angle with the zero degree and then begin counting up from zero until they reach the next arm. This will avoid incorrect scale readings. The degrees on the protractor are only labeled in multiples of ten, however each unlabeled tick represents 1°. The center point of the protractor must be placed on the vertex of the angle and the zero degree mark of the protractors baseline must be lined up with one of the angle's arms.

Some protractors have an inner scale and an outer scale. It is important to recognize that the direction of rotation between angle arms to determine which scale is used on the protractor. Always line up the zero degree with the first arm of the angle and count up to the next arm to avoid any confusion with regard to which scale should be used. The arc (hatch mark) between the arms of the angle indicates which angle is being measured.

The following diagram shows how to measure the angle ∠ABC using a protractor.
Measure Angle Protractor

How to measure angles using a protractor?
Use a full circle or half circle protractor to learn to measure angles. How to use a protractor? Measuring Angles with a Protractor How to measure an angle with a protractor? How to use a protractor to measure and draw angles? How to Use a Protractor to Measure Angles?

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