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

If you know: | Use: |

Base and altitude | "Half base times height" method |

All 3 sides | Heron's Formula |

Two sides and included angle | Side-angle-side method |

x,y coordinates of the vertices |
Area of a triangle- by formula (Coordinate Geometry) or Area of a triangle - box method (Coordinate Geometry) |

The triangle is equilateral | Area of an equilateral triangle |

- 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

- Triangle definition
- Hypotenuse
- Triangle interior angles
- Triangle exterior angles
- Triangle exterior angle theorem
- Pythagorean Theorem
- Proof of the Pythagorean Theorem
- Pythagorean triples
- Triangle circumcircle
- Triangle incircle
- Triangle medians
- Triangle altitudes
- Midsegment of a triangle
- Triangle inequality
- Side / angle relationship

- Perimeter of a triangle
- Area of a triangle
- Heron's formula
- Area of an equilateral triangle
- Area by the "side angle side" method
- Area of a triangle with fixed perimeter

- Right triangle
- Isosceles triangle
- Scalene triangle
- Equilateral triangle
- Equiangular triangle
- Obtuse triangle
- Acute triangle
- 3-4-5 triangle
- 30-60-90 triangle
- 45-45-90 triangle

- Incenter of a triangle
- Circumcenter of a triangle
- Centroid of a triangle
- Orthocenter of a triangle
- Euler line

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