Angle — 180° (Straight Angle) — free printable diagram

What is a 180 degree angle?

A 180 degree angle (180°) is a straight angle — the two arms point in opposite directions and form a straight line. This diagram shows 180° opened between two arms meeting at a vertex.

Measure

180°

Type of angle

Straight angle

Reflex angle on the other side

180°

In radians

π (≈3.142)

Fraction of a full turn

1/2 of a turn

• A 180° angle is a straight angle because the two arms point in opposite directions and form a straight line.
• Angles round a point add up to 360°, so the reflex angle on the other side of these arms measures 360° − 180° = 180°.
• In radians, 180° × π/180 = π, which is about 3.142.