Area of an equilateral triangle
The area of an equilateral triangle (all sides congruent) can be found using the formula
where s is the length of one side of the triangle.
Try this Drag the orange dots on each
vertex
to reshape the triangle. The formula shown will recalculate the area using this method.
When you know all three sides of a triangle, you can find the area using
Heron's Formula.
But in the case of equilateral triangles, where all three sides are the same length, there is a simpler formula:
where
s is the length of any side of the triangle.
Note that is constant that has the value of approximately
0.433, so the formula simplifies a little to
Methods for finding triangle area
Things to try
 In the figure above, click on "hide details"
 Drag the vertices of the triangle to make a new size triangle
 Calculate the are using this method
 Click "show details" to verify your answer
Other triangle topics
General
Perimeter / Area
Triangle types
Triangle centers
Congruence and Similarity
Solving triangles
Triangle quizzes and exercises
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