Protractor Has Entered the Building

A protractor is a device created in order to divine the degree measure of an angle or to draw an angle with a specific degree measure through the use of a circular measuring scheme. The traditional form of protractor is a semicircle with 181 markings on the outer edge, each corresponding to a certain integer degree measure from 0° to 180°. These markings point radially outward from the center of the base of the protractor, where there is a hole or other space for the placement of a writing implement. The base is a straightedge, usually marked in the same fashion as a ruler, measuring distance in millimeters or fractions of inches for your convenience. Larger protractors tend to have a semicircular hole in the middle for portability and lightness. A protractor can be made from a plethora of materials, including wood, steel, paper or plastic, depending on its intended purpose.

Making and Measuring Angles with Protractors

To make an angle, select a location on your paper for the vertex of the two lines you are about to create. Place the center point of the base of the protractor on this point, and hold it there firmly in place with your less-dexterous hand. With your other hand, using a pen or pencil (or something else if you like), make a mark at the center point, the 0° mark, and the mark on the perimeter corresponding to the degree measure you desire. Warning! You may see two rows of numbers on your protractor: Do not be alarmed. It doesn't matter which row you use as long as you always use the same one. Now, remove the protractor and connect the dots using a straightedge. Having a protractor with a straightedge for a base significantly speeds up this step.

To measure an angle, place the center point above the vertex of the two lines and align one line with the base of the protractor, such that the other line travels under the protractor. This line will pass close to or through one of the degree markers on the outside of the protractor. If the line parallel to the base passes through 0°, then this is the degree measure of the angle. If the line parallel to the base passes through 180°, then subtract the number from 180 to get the final degree measure.

Protractors in the Classroom

As a student of trigonometry, an aspiring mathematician is furnished with a protractor, generally made of plastic. Some such protractors have a swing arm bar that rotates about the central point of the circle, which lets the student draw the line from the center point to the degree mark without using an additional ruler. A paper protractor may also be used, but is best laminated to protect it from serious damage. The teacher may also have a large wooden protractor for chalkboard demonstrations.

Protractors in the Workplace

Protractors find most of their use outside of academia. Architects use protractors when drawing up plans and carpenters use protractors whenever they make buildings other than rectangular boxes. The architect's protractor is generally small, flat and plastic for increased accuracy and range of use. The builder's protractor is made of steel for increased durability. Some carpenters use digital protractors, which are truly a miracle of modern science. A digital protractor consists of two large metal bars attached at one end by a hinge. When the bars are rotated apart, an internal computer calculates and displays the angle between the two bars. It's a geometer's wet dream come true.

Protractors on the Battlefield

A steel protractor is preferred in all combat situations. It is a good idea to equip the base of your protractor with a handle for sturdier gripping. You should also sharpen the outside edge of your protractor for increased destructive power.

A protractor can deflect attacks from a variety of weapons, including swords, clubs, claws and some projectiles. See the Klingons in Star Trek: The Next Generation.
Hand-to-Hand Combat
A protractor functions the same way that brass knuckles do in close combat, except with the added ability to pierce. Aim for the head, neck and gut for greatest bodily injury.
Long-Range Combat
A protractor makes an excellent projectile. See Xena, Warrior Princess.

Protractors at Play

Protractors make excellent toys. You can use a protractor like a frisbee, although more care is necessary due to the lack of sufficient weight and surface area. With proper modifications, a protractor will behave like a boomerang. A protractor can also be used as a substitute for other playthings in games like Kill the Carrier (everyone chases the person with the protractor with the intent of taking it from them by force) and Kick the Protractor (see Kick the Can, except replace "can" with "protractor"). Pre-adolescents have also been known to play Spin the Protractor (see Spin the Bottle, except that a protractor is spun, and the target is the person who, when the protractor stops spinning, is being pointed at by a specific degree measure, say, 69°).

Pro*tract"or (?), n.


One who, or that which, protracts, or causes protraction.


A mathematical instrument for laying down and measuring angles on paper, used in drawing or in plotting. It is of various forms, semicircular, rectangular, or circular.

3. Surg.


4. Anat.



An adjustable pattern used by tailors.



© Webster 1913.

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