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Jessica Kaminski

7 minutes read

May 10, 2022

How to Use a Protractor?

Teaching

By the 4th grade, kids begin learning types of angles. They advance to measuring angles with the help of tools like a protractor. But for many children, a protractor is a confusing semicircle with dashes and numbers, so they need detailed guidelines to learn how to use a protractor to measure and draw angles.

What Is a Protractor?

A protractor is one of those mathematical instruments your child learns about while understanding shapes’ concepts and properties. A protractor is a semicircular tool that measures angles from 0 to 180 degrees. It comes with numbers on both sides of its body to give different values during measurement. You can also take readings from inside or outside the protractor.

When children use a protractor, they solidify their knowledge of drawing, measurement, and even recognition of angles. Through hands-on activities, you can introduce a protractor to your child and have them note the numbers on the protractor and the way they move in clockwise and anticlockwise manners from 0 to 180 degrees.

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How to Read a Protractor

Before you can correctly read a protractor, you need to understand every part of the mathematical tool. Here are some of the essential components of a protractor:

Baseline

The baseline of a protractor is a horizontal line at the bottom, also referred to as the reference point. A vertical line bisects the baseline of a protractor at its center point. Since the baseline has two sides, they are called left and right-side baselines.

Origin

The origin of a protractor is a point where the baseline and the perpendicular line meet at the bottom. A vertical line cuts the baseline precisely at the protractor’s baseline; so, a protractor’s origin is also called the center or midpoint.

Degree scale

When your child first handles a protractor, they may notice long and short lines. Each short line inside a semicircle represents a degree, and the total number of degrees is one hundred and eighty(180). There are tiny line segments for every one degree (1), and there are more line segments of substantial size for every five (5) and ten degrees (10) in between.

An inner degree scale shows the anticlockwise rotation of the numbers from 0 to 180 from the right side of the protractor. The outer degree scale shows the clockwise rotation of the numbers from 0 to 180 from the left side of the semicircular degree scale.

How to Use a Protractor?

Before you get down to using a protractor, you must introduce popular definitions of angle measurements to students. Let them know what right, obtuse, acute, vertex, or arc angles are. A right angle is a 90-degree angle with a squared appearance that takes the shape of a letter L. For example, an acute angle is greater than 0 degrees but less than 90 degrees. Obtuse angles refer to angles greater than 90 degrees but less than 180 degrees.

How to Use a Protractor to Measure Angles

Before measuring angles with protractors, estimate the angle you are looking for and determine if it is an acute, obtuse, or right angle. Remember that you can classify angles as acute if they are less than 90 degrees and obtuse when they are above 90 degrees. While measuring angles with a protractor, the kind of angle you want to measure should be apparent to the naked eye. However, you must use a protractor to confirm your speculation on the exact angle.

The second step in measuring angles using a protractor is to place the origin directly above the vertex or center point. Gently move the protractor to the baseline while keeping the vertex (the area where the angle lines travel outwards like sun rays) in the same line as the origin.

Follow the measurements up to the angles on each side of the protractor’s arc. Your child can measure angles with a protractor and determine the angle’s degree measurement by the number through which the line passes.

How to Use a Protractor to Draw Angles

Start using a protractor by drawing a straight horizontal line on paper that should serve as your angle’s starting point. Place the origin of your protractor at the beginning of the line and locate where your lines should meet. Make a mark on the paper to indicate the vertex’s location.

To determine angles on a protractor, place a dot or dash on the degree scale you want to follow through. If you plot angles less than 90 degrees, use the degree scale with smaller numbers. If the angles are greater than 90 degrees, you can use the part of the degree scale with bigger digits.

Finally, connect the vertex to the specified degree using a ruler. Or, you can use the straight edge of your protractor to draw the second line, then use your protractor to confirm the angle.

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How to Find the Degree of an Angle without a Protractor

If you don’t have a protractor at home, you do not need to panic. You can download this printable protractor in PDF format. This improvised tool is handy if all the scales are intact because you can make various copies. So, if your child damages any, you can get a new one for them to continue practicing.

A printable protractor can build your child’s enthusiasm for the real thing. However, educators do not advise parents to search for online protractor and print it because the measurements may be off. Sometimes, you may end up with degree scales that are either less or more than those on a standard protractor.

Even though using a protractor with angles is the simplest way to pinpoint degrees in geometry, you may not have access to one. If that is the case, the fundamental geometric concepts of triangles can come in handy using a scientific calculator. You can get free online calculators and apps from your mobile app store or the internet. Plus, you can do a quick google search or watch YouTube videos to find other alternatives.

Conclusion

As kids advance, they learn new math concepts like angles and measurements. But without a tool, they may struggle with the new ideas their math teachers introduce. They need guides like this to teach them to use a geometry protractor to get a visual representation of angles.

Jessica Kaminski

Jessica is a a seasoned math tutor with over a decade of experience in the field. With a BSc and Master's degree in Mathematics, she enjoys nurturing math geniuses, regardless of their age, grade, and skills. Apart from tutoring, Jessica blogs at Brighterly. She also has experience in child psychology, homeschooling and curriculum consultation for schools and EdTech websites.