The Lesson

Degrees are a unit of measurement of an angle. There are 360 degrees in a full rotation.

Dictionary Definition

The Oxford English Dictionary defines a degree as "a unit of measurement of angles or circular arcs, being an angle equal to the 90th part of a right angle, or an arc equal to the 360th part of the circumference of a circle (which subtends this angle at the centre)."

A Real Example of Degrees

An angle measured in degrees is written as number followed by the degree symbol °:

90 degrees This is 90° (said as "90 degrees").

360 Degrees in a Circle

There are 360 degrees in a full rotation (a circle). One degree is 1⁄360th of a circle.

a degree is 1 360th of a turn

How to Measure an Angle in Degrees

The number of degrees in an angle can be measured directly using a protractor:

measure a degree with a protractor Alternatively, geometry and trigonometry can be used to find angles.

Important Angles in Degrees

  • 90° is a right angle, a quarter of a rotation.

    90 degrees is a quarter turn
  • 180° is a straight angle, a half of a rotation.

    180 degrees is a half turn
  • 270° is three quarters of a rotation.

    270 degrees is three quarters of a turn
  • 360° is a full angle, a whole rotation.

    360 degrees is a whole turn