Enter any single angle of the angles between parallel lines into the calculator to determine the missing three angles.

Vertical Angle Formula

The following formula is used to calculate vertical angle pairs.

A=C , B=D

A= abs (b-180)

  • Where A,B,C,and D are the vertical angles described in the diagram below.
vertical angles

Vertical Angle Definition

What are vertical angles? Vertical angles are two opposite angles created by intersecting lines. In the diagram above, A and C are vertical angles and B and D are vertical angles. Vertical angles are always equal to one another. (A=C).


How to calculate vertical angles?

  1. First, determine one given angle.

    First, this example, an angle A is given as 30 degrees.

  2. Using the formula above, determine the rest of the angles.

    Since C is equal to A, C = 30 degrees. B = abs (30-180) = 150. Since D is equal to B then D = 150. The final answer is A=30, C=30, B=150, D=150

Vertical Angles

Are vertical angles congruent? By definition, vertical angles are considered congruent angles, since the only requirement of congruent angles is that they are equal. This is the same as the definition for vertical angles.

Are vertical angle supplementary? A pair of vertical angles do not have to be supplementary, although they can be if they are equal to 90 degrees each.

Are vertical angles complementary? Vertical angles are only complementary when they are equal to 45 degrees, however, the sum of a vertical angle and the other vertical angle of two intersecting lines are always complimentary.

vertical angle calculator
vertical angle formula