Discover the type of any triangle—equilateral, isosceles, or scalene—instantly by inputting its three side lengths. This essential geometry tool helps students and enthusiasts quickly classify triangles based on their side properties, including a validity check.
Formula:
How to Determine Triangle Type by Sides
A triangle's type is determined by comparing the lengths of its three sides (let's call them a, b, and c):
- Equilateral Triangle: All three sides are equal. Formula:
a = b = c - Isosceles Triangle: Exactly two sides are equal. Formula:
(a = b) OR (b = c) OR (a = c)(but not all three) - Scalene Triangle: All three sides are different lengths. Formula:
a ≠ b ≠ c ≠ a
Important: For a valid triangle to form, the sum of the lengths of any two sides must be greater than the length of the third side (Triangle Inequality Theorem: a + b > c, a + c > b, b + c > a). Our calculator checks this automatically.