Square Footage of a Triangle (three sides)

The Area of a Triangle with three known Sides calculator computes the area of a triangle based on the length of its three sides.

INSTRUCTIONS: Choose units and enter the following:

• (a) Length of Side a 
• (b) Length of Side b
• (c) Length of Side c 

Area of Triangle (A): The calculator returns the area in square feet (ft²).  However, this can be automatically converted to other area units (e.g. square meters) via the pull-down menu.

The Math / Science

The formula for the area of a triangle base on the length of its three side is:

`A = sqrt((a+b+c)/2((a+b+c)/2-a)((a+b+c)/2-b)((a+b+c)/2-c))`

where:

• A = area of triangle
• a = length of side a
• b = length of side b
• c = length of side c  

A note on Triangles: The calculator checks that no one side is greater than the sum of the other two.  In that case, it is impossible to have a triangle.

(a+b+c)/2 is often referred to as the semi-perimeter of a triangle.