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Measuring and Drawing Angles

Related Topics: More Geometry Lessons


In this lesson, we will learn
  • what is a protractor.
  • how to measure angles using a protractor.
  • how to draw angles using a protractor.
Interactive activities are included to help you practice measuring angles with a protractor.

Measuring Angles

The size of an angle is usually measured in degrees (°). Think of a circle which is divided into 360 equal sectors. Each sector has a small angle at the centre of the circle – the size of such angle is 1 degree (written: 1°). In other words, the size of an angle is a measure of how wide the angle is at the vertex bound by the two sides.

Given an angle ABC ,


How do we measure the size of the angle? We can measure angles using an instrument known as a protractor.

What is a protractor?

A protractor is an instrument used to measure the size of angles.

The protractor shown below has two scales:
The outer scale starts from 0˚ to180˚ going clockwise.
The inner scale starts from 0˚ to 180˚ going anti-clockwise.

protractor outer inner scale

How to measure an angle using a protractor

To measure angle ABC , we need to:

Step 1: Place the center point of the protractor on the vertex B.
Step 2: Adjust the base line of the protractor so that it is aligned with the line BC
Step 3: Read the value of angle ABC, from the inner scale.

protractor measure angle

We can also adjust the base line of the protractor so that it is aligned with the line AB and use the outer scale to measure the angle.

protractor angle

How to measure and draw angles using a protractor?

The following videos will show you how to measure and draw angles using a protractor.

Measuring and Drawing Angles
How to measure angles and draw angles using a protractor?
Measuring angles using a protractor (acute angles)
Measuring Angles with Protractors (obtuse angles)

Activities using a Protractor

Using a Protractor
Explore how to use a protractor

Angle Measure
Drag and drop the Protractor to measure the angle

Measuring Angles
Practice lining up and reading a protractor while you measure a set of angles in this fun learning activity. The angles may range from 0° to 180°.

Guess the Angle
Determine the acute or obtuse angle.

Rotate to landscape screen format on a mobile phone or small tablet to use the Mathway widget, a free math problem solver that answers your questions with step-by-step explanations.

You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

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