Supplementary Angles Calculator

What Are Supplementary Angles?

Two angles are supplementary when they add up to $180°$ (or $\pi$ radians). If placed adjacent, they form a straight line.

Given angle $\alpha$, the supplement $\beta$ is:

$$\beta = 180° - \alpha \quad \text{or} \quad \beta = \pi - \alpha$$

Add the two angles. If $\alpha + \beta = 180°$, they are supplementary.

For supplementary angles $\alpha$ and $\beta$:

Can two acute angles be supplementary?

No. Two acute angles sum to less than 180°. Supplementary pairs are either one acute and one obtuse, or both right angles (90° each).

Are 30° and 150° supplementary?

Yes. 30° + 150° = 180°, so they form a straight angle when adjacent.

What is the supplement of 120°?

180° - 120° = 60°.

How are supplementary angles different from complementary angles?

Complementary angles sum to 90°. Supplementary angles sum to 180°.