Enter any angle in degrees or radians into the calculator to determine the complementary angle.

## Complementary Angle Formula

The following formula is used to calculate a complementary angle.

A = 90-a

- Where A is the complementary angle (degrees)
- a is the original angle (degrees)

## Complementary Angle Definition

A set of complementary angles is defined as any two angles that when added together will equal 90 degrees.

## How to calculate a complementary angle?

- First, determine the initial angle. If measure in radians, multiply by 57.29 to get the angle in degrees.
- Next, use the formula above to calculate the complementary angle.
- For example, if the initial angle given was 25 degrees, then the complementary angle would be: 90-25 = 65 degrees.

## FAQ

**What is a complimentary angles?**

A set of complimentary angles have a sum of 90 degrees.

**Can complementary angles be negative?**

Yes, complementary angles can be negative. For example, if one angle is 120 degrees then the complimentary angle is -30 degrees since 120 + (-30) = 90.

**Can complementary angles be equal to each other?**

The only complimentary angles that will be equal to each other are 45 degrees and 45 degrees. (45+45=90).

**Do complementary angles share a common side?**

Complementary angles can share a common side when they lie in the first quadrant. For example, an angle of 70 and 20 would share a common side.

**Are complementary angles always congruent?**

Complementary angles are only congruent when they equal each other.

**Can complementary angles make a right triangle?**

Complementary angles will always make a right triangle when added together. By definition, their sum will be 90 degrees.