Triangle Angle Calculator Formula

Understand the math behind the triangle angle calculator. Each variable explained with a worked example.

Use the Triangle Angle Calculator

Formulas Used

Angle C

angle_c = 180 - angle_a - angle_b

Sum Check

sum_check = angle_a + angle_b + (180 - angle_a - angle_b)

Triangle Type

triangle_type = (angle_a == 90 or angle_b == 90 or (180 - angle_a - angle_b) == 90) ? 1 : 0

Variables

VariableDescriptionDefault
angle_aAngle A(degrees)60
angle_bAngle B(degrees)70

How It Works

How to Find a Missing Triangle Angle

Formula

Angle C = 180° - Angle A - Angle B

The sum of all interior angles of a triangle is always 180 degrees. If you know two angles, you can find the third by subtracting their sum from 180.

Triangle Types by Angles

  • Acute: All angles less than 90°
  • Right: One angle exactly 90°
  • Obtuse: One angle greater than 90°

    • Worked Example

    A triangle has angles of 60° and 70°. Find the third angle.

    angle_a = 60angle_b = 70
    1. 01Angle C = 180° - 60° - 70°
    2. 02= 180° - 130°
    3. 03= 50°

    Ready to run the numbers?

    Open Triangle Angle Calculator