A 180° angle is a straight angle: the two arms point in exactly opposite directions and form a straight line. It is exactly half of a full turn and equal to two right angles.
180° is one half (1/2) of a full circle, or π radians. The minute hand of a clock sweeps 180° in 30 minutes. If you face north and turn 180° clockwise, you end up facing due south (S).
180° angle facts
| Angle type | Straight angle (exactly 180°) |
|---|---|
| Explement (adds to 360°) | 180° |
| Radians | π ≈ 3.141593 |
| Gradians | 200 grad |
| Fraction of a turn | one half (1/2) (50%) |
| Degrees, minutes, seconds | 180° 0′ 0″ |
| Compass bearing | south (S) |
Trigonometric values of 180°
| Function | Value |
|---|---|
| sin 180° | 0 |
| cos 180° | −1 |
| tan 180° | 0 |
180° on a protractor
How to draw a 180° angle with a protractor
- Draw a straight line with a ruler.
- Mark a point on the line: this is the vertex.
- The two halves of the line are the arms of a 180° angle. Draw a half-circle arc over the vertex and label it 180°.
Where you see 180° angles
- A straight line, like a flat horizon or a tabletop edge, is a 180° angle.
- At 6:00 the hands of a clock point in opposite directions: 180°.
- Carbon dioxide (CO₂) is a linear molecule with a 180° bond angle.
- The Earth turns 180° on its axis in about 12 hours.
Related angles
180° angle FAQ
What type of angle is 180°?
A 180° angle is a straight angle, because it is exactly 180°.
Does a 180° angle have a complement or supplement?
No. Complements add up to 90° and supplements to 180°, and 180° is already equal to 180°. What it does have is an explement (conjugate) of 180°, the angle that completes a full 360° circle.
How many radians is 180 degrees?
180° = π radians ≈ 3.1416 rad. To convert degrees to radians, multiply by π/180: 180 × π/180 = π.