Triangle Calculator

To find area & perimeter of triangle, input length (l), breadth (b), and click calculate button using triangle calculator 

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What is a Triangle?

A triangle is a plane figure with straight sides and three angles. All of the interior angles add up to 180 degrees. A triangle is a polygon with three corners or vertices and three sides or edges which are line segments. A triangle with vertices A, B, and C is denoted ABC.

A triangle is a three-sided polygon consisting of three line segments linked end-to-end.

  • The interior angles of a triangle always add up to 180 degrees
  • The exterior angles of a triangle always add up to 360 degrees


  1. Area of a triangle: [l × b /2]
  2. Perimeter of Triangle: [(a + b + c)]
  3. Area of Equilateral Triangle: [(Sqrt (3)/4)×(side)²]
  4. Area of Triangle SAS (2sides & opposite angle): [½×a×b×SinC]


  • l = length
  • b =breadth
  • a,b, and c = sides of the triangle

Types of Triangle

There are seven types of triangles:

  • Isosceles triangle
  • Equilateral triangle
  • Scalene triangle
  • Right angle triangle
  • Obtuse triangle
  • Acute triangle
  • Equiangular

How to calculate the area & perimeter of a triangle?

Example 1:

Calculate the area of a triangle with a given length of 3 and breadth of 4 cm.


length = l = 3

breadth = b = 4 cm

Take the formula and substitute the above values

Area = [l × b /2]

= (3*4/2) = 12/2 = 6

Example 2:

Calculate the Perimeter of a triangle with the given sides as 3, 4, and 5 cm.


a = 3 cm

b = 4 cm

c = 5 cm

Take the formula and substitute the above values

Perimeter = a + b + c

Perimeter = 3 + 4 + 5 = 12

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