Astar Protractor 180 Degree SL-1 (152mm)

A protractor is a measuring instrument, typically made of transparent plastic or glass, for measuring angles.

Some protractors are simple half-discs. More advanced protractors, such as the bevel protractor, have one or two swinging arms, which can be used to help measure the angle.

Most protractors measure angles in degrees (°). Radian-scale protractors measure angles in radians. Most protractors are divided into 180 equal parts. Some precision protractors further divide degrees into arcminutes.

They are used for a variety of mechanical and engineering-related applications. One common use is in geometry lessons in schools.