Triangle Angle Calculator

Enter 1 or 2 known angles of a triangle to find the missing angle(s). The calculator also classifies the triangle type.

Enter Known Angles

Result

Missing Angle
50°
degrees
Angle A60°
Angle B70°
Angle C50°
Triangle TypeAcute
Angle Sum180°

Step-by-Step Solution

A + B + C = 180° => C = 180° - 60° - 70° = 50°

Triangle Angle Sum Property

The sum of the interior angles of any triangle is always 180 degrees. This fundamental property allows you to find a missing angle when you know the other two. This rule applies to all triangles regardless of size, shape, or type.

Acute Triangle

All three angles are less than 90 degrees.

A < 90, B < 90, C < 90

Right Triangle

One angle is exactly 90 degrees.

One angle = 90°

Obtuse Triangle

One angle is greater than 90 degrees.

One angle > 90°

Equilateral Triangle

All three angles are exactly 60 degrees.

A = B = C = 60°

How to Find Missing Triangle Angles

If you know two angles A and B, the third angle C = 180 - A - B. For any valid triangle, each angle must be greater than 0 degrees and less than 180 degrees, and all three must sum to exactly 180 degrees.

Classification Rules

  • Equilateral: All angles equal 60°
  • Isosceles: Two angles are equal
  • Scalene: All angles are different
  • Right: One angle is exactly 90°
  • Acute: Largest angle < 90°
  • Obtuse: Largest angle > 90°