Finds the angle that, added to a given angle, sums to exactly 180 degrees.
How it works
The given angle is subtracted from 180 degrees.
What this does not include
This does not include finding an angle that sums to 90 degrees instead — for that different pairing, use this site’s complementary angles calculator instead.
How to use this calculator
- Enter an angle between 0 and 180 degrees.
A worked example
An angle of 110° has a supplement of 180 − 110 = 70°.
An angle of 45° has a supplement of 135°.
What the variables mean
| Variable | Meaning |
|---|---|
| Angle | A given angle, between 0° and 180° |
| Supplement | The angle that, added to the given one, totals 180° |
Edge cases worth knowing
An angle of 200° has no valid supplement — supplementary pairs are defined between 0° and 180°, since a supplement itself can’t be negative.
Two right angles (90° each) are their own supplements — the only case where an angle and its supplement are identical.
Frequently asked questions
What’s a real-world example of supplementary angles?
Two angles that together form a straight line are always supplementary, since a straight line measures exactly 180 degrees.
Is 90 degrees a special case?
Yes — 90 degrees is its own supplement, since 90 + 90 = 180.
Can two supplementary angles both be obtuse?
No — since they must sum to 180 degrees, at most one of the pair can be 90 degrees or more; if one is obtuse, the other must be acute.
