In geometry, a protractor is a circular or semicircular tool for measuring an angle or a circle. The units of measurement utilized are usually degrees.

Some protractors are simple half-discs; these have existed since ancient times. More advanced protractors, such as the Bevel Protractor have one or two swinging arms, which can be used to help measure the angle.

External Protractors are instruments used on spheres to find a certain number of degrees. There are all different types of protractors, and they are used to find angles.

Protractors are included as school supplies.

Bevel Protractor

A Bevel Protractor is a graduated circular protractor having a pivoted arm; used for measuring or marking off angles. Sometimes vernier scales are attached to give more accurate readings. It has wide application in architectural and mechanical drawing although with the availability of modern drawing software or CAD the tool is less commonly used in that sphere.

Universal Bevel Protractors are also used by toolmakers, as they measure angles by mechanical contact they are classed as mechanical protractors. [cite book
last = Farago
first = Francis T
authorlink =
coauthors = Curtis
title = Handbook of Dimensional Measurement
publisher = Industrial Press Inc
date = 1994
location =
pages = 580
url =,M1
doi =
id =
isbn = 0831130539


See also

* Protractor compass
* Goniometer
* Geometry template


External links

* [ More printable protractors]
* [ How to measure angles with a protractor] An interactive animation
* [ How to draw angles with a protractor] An interactive animation
* [ Angle definition pages] with interactive applets that are also useful in a classroom setting. Math Open Reference
* [] Picture of bevel protector.
* [] Different bevel protectors.
* [ Inspection Methods - Angular Measurement]

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Look at other dictionaries:

  • Protractor — Pro*tract or, n. 1. One who, or that which, protracts, or causes protraction. [1913 Webster] 2. A mathematical instrument for laying down and measuring angles on paper, used in drawing or in plotting. It is of various forms, semicircular,… …   The Collaborative International Dictionary of English

  • protractor — PROTRACTÓR, OÁRE adj., s. m. (muşchi) care are rolul de a întinde un membru sau o parte a corpului spre înainte. (< fr. protracteur) Trimis de raduborza, 15.09.2007. Sursa: MDN …   Dicționar Român

  • protractor — 1610s, one who lengthens (an action), agent noun from L. protrahere (see PROTRACT (Cf. protract)); sense of instrument for drawing angles first recorded 1650s …   Etymology dictionary

  • protractor — the instrument used in geometry, is spelt or, not er …   Modern English usage

  • protractor — ► NOUN ▪ an instrument for measuring angles, typically in the form of a flat semicircle marked with degrees along the curved edge …   English terms dictionary

  • protractor — [prō′trak΄tər, prō trak′tər] n. [ML] 1. a person or thing that protracts 2. an instrument in the form of a graduated semicircle, used for plotting and measuring angles 3. Anat. a muscle that protracts, or extends, a limb …   English World dictionary

  • protractor — /proh trak teuhr, preuh /, n. 1. a person or thing that protracts. 2. (in surveying, mathematics, etc.) an instrument having a graduated arc for plotting or measuring angles. 3. Anat. a muscle that causes a part to protrude. [1605 15; < ML; see… …   Universalium

  • protractor —    A semicircular tool for the measurement and construction of angles. On the flat side of the protractor in the middle is either a hole or cross hairs. This is where the vertex (point of the angle) must go when measuring. Usually a horizontal… …   Glossary of Art Terms

  • protractor — matlankis statusas T sritis Standartizacija ir metrologija apibrėžtis Įtaisas kampams matuoti ir žymėti brėžinyje. atitikmenys: angl. angle protractor; protractor; semicircular protractor vok. Winkelmesser, n rus. транспортир, m pranc. demi… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • protractor — matlankis statusas T sritis fizika atitikmenys: angl. angle protractor; protractor; semicircular protractor vok. Transporteur, m; Winkelmesser, n rus. транспортир, m pranc. demi cercle gradué, m; rapporteur, m …   Fizikos terminų žodynas

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