What is an angle?

An angle is the measure of rotation between two rays that share a common endpoint, called the vertex. Angles are most commonly expressed in degrees (°), where a full rotation equals 360°, or in radians (rad), where a full rotation equals 2π. Understanding angles is fundamental to geometry, trigonometry, architecture, engineering, and many everyday tasks involving direction or rotation.

Angles are classified by their size: acute angles are less than 90°, right angles are exactly 90°, obtuse angles are between 90° and 180°, straight angles are exactly 180°, and reflex angles are between 180° and 360°.

Tool description

The Angle Measurer is an interactive visual tool for exploring and measuring angles. It renders a draggable two-arm angle diagram on a canvas. You can drag the movable arm to any position to set the angle, or type an exact value in degrees or radians. The tool instantly shows the angle type, its complementary angle, its supplementary angle, and the equivalent value in the other unit.

Features

  • Interactive drag control — click or drag anywhere on the canvas to set the angle visually.
  • Dual unit input — enter the angle in degrees or radians; both fields stay in sync automatically.
  • Angle classification — instantly identifies the angle type (acute, right, obtuse, straight, reflex, or full).

Options explained

Field Description
Degrees input Enter any value from 0 to 360. Values outside this range are automatically normalized.
Radians input Enter the angle in radians (e.g. 1.5708 for 90°).
Complementary The angle needed to reach 90°. Only shown when the angle is ≤ 90°.
Supplementary The angle needed to reach 180°. Only shown when the angle is ≤ 180°.
Angle type Classification label: acute, right, obtuse, straight, reflex, or full.