Area of Triangle Calculator

Calculate triangle area with multiple methods. Free online triangle area calculator using base-height, sides, or coordinates.

The Area of Triangle Calculator finds the area using multiple methods: base and height, three sides (Heron's formula), or coordinates. This versatile geometry tool handles all triangle types—right, acute, obtuse, equilateral, isosceles, or scalene. Perfect for geometry homework, construction, surveying, and design applications where triangular shapes appear.

Common use cases

  • Geometry homework and tests
  • Roof pitch calculations
  • Land surveying triangulation
  • Sail and flag design
  • Architectural triangular features

How to use

  1. Choose your input method
  2. Enter the required measurements
  3. Click calculate for the area
  4. View the formula used
  5. Try alternative methods to verify

FAQ

What is the basic triangle area formula?

Area = ½ × base × height. The height must be perpendicular to the base.

What is Heron's formula?

Area = √(s(s-a)(s-b)(s-c)) where s = (a+b+c)/2 is the semi-perimeter and a,b,c are side lengths.

How do I find area from coordinates?

Area = ½|x₁(y₂-y₃) + x₂(y₃-y₁) + x₃(y₁-y₂)| using the vertices (x₁,y₁), (x₂,y₂), (x₃,y₃).

What if I only know two sides and an angle?

Area = ½ × a × b × sin(C) where C is the angle between sides a and b.