Area of Equilateral Triangle
The area of an equilateral triangle is the amount of space that an equilateral triangle covers in a 2dimensional plane. An equilateral triangle is a triangle with all sides equal and all its angles measuring 60º. The area of any shape is the number of unit squares that can fit into it. Here, "unit" refers to one (1) and a unit square is a square with a side of 1 unit. Alternatively, the area of an equilateral triangle is the total amount of space it encloses in a 2dimensional plane.
What is the Area of an Equilateral Triangle?
The area of an equilateral triangle is defined as the region covered within the three sides of the triangle. It is expressed in square units. Some important units used to express the area of an equilateral triangle are in^{2}, m^{2}, cm^{2}, yd^{2}, etc. Let us understand the formula to calculate the area of an equilateral triangle and its derivation in the sections below.
Area of an Equilateral Triangle Formula
The equilateral triangle area formula is used to calculate the space occupied between the sides of the equilateral triangle in a 2D plane. Calculating areas of any geometrical shape is a very important skill used by many people in their work. For the equilateral triangle, we have the formula for its area. In a general triangle, finding the area of a triangle might be a little bit complicated for certain reasons. But, finding the area of an equilateral triangle is quite an easy calculation.
The general formula for the area of a triangle whose base and height are known is given as:
Area = 1/2 × base × height
While the formula to calculate the area of an equilateral triangle is given as,
Area = √3/4 × (side)^{2} square units
In the given triangle ABC, Area of ΔABC = (√3/4) × (side)^{2} square units, where, AB = BC = CA = a units (the length of equal sides of the triangle).
Thus, the formula for the area of the above equilateral triangle can be written as:
Area of equilateral triangle ΔABC = (√3/4) × a^{2} square units
Example: How to find the area of an equilateral triangle with one side of 4 units?
Solution:
Using the area of equilateral triangle formula: (√3/4) × a^{2} square units,
we will substitute the values of the side length.
Therefore, the area of the equilateral triangle (√3/4) × 4^{2} = 4√3 square units.
Derivation of Area of an Equilateral Triangle Formula
In an equilateral triangle, all the sides are equal and all the internal angles are 60°. So, an equilateral triangle’s area can be calculated if the length of one side is known. The formula to calculate the area of an equilateral triangle is given as,
Area of an equilateral triangle = (√3/4) × a^{2} square units
where,
a = Length of each side of an equilateral triangle
The above formula to find the area of an equilateral triangle can be derived in the following ways:
 Using the general area of a triangle formula
 Using Heron's formula
 Using trigonometry
Deriving Equilateral Triangle's Area Using Area of Triangle Formula
The formula used to calculate the area of an equilateral triangle can be derived using the general area of the triangle formula. To do so, we require the length of each side and the height of the equilateral triangle. We will thus calculate the height of an equilateral triangle in terms of the side length.
The formula for the area of an equilateral triangle comes out from the general formula of the area of the triangle which is equal to ½ × base × height. Derivation for the formula of an equilateral triangle is given below.
Area of triangle = ½ × base × height
For finding the height of an equilateral triangle we use the Pythagoras theorem (hypotenuse^{2 }= base^{2} + height^{2}).
Here, base = a/2, height = h, and hypotenuse = a (refer to the above figure).
Now, apply the Pythagoras theorem in the triangle.
a^{2} = h^{2} + (a/2)^{2}
⇒ h^{2} = a^{2} – (a^{2}/4)
⇒ h^{2} = (3a^{2})/4
Or, h = ½(√3a)
Now, put the value of “h” in the area of the triangle equation.
Area of Triangle = ½ × base × height
⇒ A = ½ × a × ½(√3a) [The base of the triangle is 'a' units]
Or, area of equilateral triangle = ¼(√3a^{2})
So, the formula of height comes as ½ × (√3 × side), and further, the area of the equilateral triangle becomes √3/4 × side^{2 }square units.
Deriving Area of Equilateral Triangle Using Heron's Formula
Heron's formula is used to find the area of a triangle when the lengths of the 3 sides of the triangle are known. In mathematics, Heron's formula is named after Hero of Alexandria, who gives the area of any triangle when the lengths of all three sides are known. We do not use angles or other distances for finding the area of a triangle using Heron's formula.
Steps are given below for finding the area of a triangle:
Consider the triangle ABC with sides a, b, and c. Heron's formula to find the area of the triangle is:
Area = √s(s  a)(s  b)(s  c)
where,
s is the semiperimeter which is given by:
s = (a + b + c)/2
For equilateral triangle: a = b = c.
s = (a + a + a)/2
s = 3a/2
Now, Area of equilateral triangle = \(\sqrt {s(s  a)(s  a)(s  a)}\)
= \(\sqrt {\frac{{3a}}{2}(\frac{{3a}}{2}  a)(\frac{{3a}}{2}  a)(\frac{{3a}}{2}  a)}\)
= \(\sqrt {\frac{3a}{2}(\frac{{a}}{2})(\frac{{a}}{2})(\frac{{a}}{2})}\)
= \(\sqrt{\frac{3a}{2}(\frac{{a^3}}{8}})\)
=\(\sqrt{({\frac{{3a^4}}{16}})}\)
Area of equilateral triangle = √3/4 × (side)^{2} square units.
Deriving Area of Equilateral Triangle With 2 Sides and Included Angle (SAS)
For finding the area of a triangle with 2 sides and the included angle, use the sine trigonometric function to calculate the height of a triangle and use that value to find the area of the triangle. There are three variations to the same formula based on which sides and included angle are given.
Consider a, b, and c are the different sides of a triangle.
 When sides 'b' and 'c' and included angle A is known, the area of the triangle is: 1/2 × bc × sin(A)
 When sides 'b' and 'a' and included angle C is known, the area of the triangle is: 1/2 × ab × sin(C)
 When sides 'a' and 'c' and included angle B is known, the area of the triangle is: 1/2 × ac × sin(B)
In an equilateral triangle, ∠A = ∠B = ∠C = 60°. Therefore, sin A = sin B = sin C. Now, area of △ABC = 1/2 × b × c × sin(A) = 1/2 × a × b × sin(C) = 1/2 × a × c × sin(B).
For equilateral triangle, a = b = c (refer to the above figure).
Area = 1/2 × a × a × sin(C) = 1/2 × a^{2} × sin(60°) = 1/2 × a^{2} × √3/2
So, area of equilateral triangle = (√3/4)a^{2} square units.
How to Find the Area of Equilateral Triangle?
The following steps can be followed to find the area of an equilateral triangle using the side length:
 Step 1: Note the measure of the side length of the equilateral triangle.
 Step 2: Apply the formula to calculate the equilateral triangle's area given as, A = (√3/4)a^{2}, where, a is the measure of the side length of the equilateral triangle.
 Step 3: Express the answer with the appropriate unit.
Now, that we have learned the formula and method to calculate the area of the equilateral triangle, let us see a few solved examples for better understanding.
Examples on Area of Equilateral Triangle

Example 1: An equilateral triangle signboard needs to be painted in red color. Each side of the signboard measures 8 in. Find the area to be painted red.
Solution:
The area of an equilateral triangle is given as,
Area = √3/4 × (Side)^{2}
By substituting the value of sidelength in the above formula, we get,
= √3/4 × 8^{2}
= 16√3
Therefore, Area to be painted red = 16√3 inches^{2}.
Answer: Area to be painted red = 16√3 inches^{2}.

Example 2: Using the equilateral triangle area formula, calculate the area of an equilateral triangle whose each side is 12 in?
Solution:
Given: Side = 12 in
Using the equilateral triangle area formula,
Area = √3/4 × (Side)^{2}
= √3/4 × (12)^{2}
= 36√3 in^{2}
Therefore, the equilateral triangle area is 36√3 in^{2}.
Answer: Area of the given equilateral triangle = 36√3 in^{2}.
FAQs on Area of an Equilateral Triangle
What is the Area of an Equilateral Triangle in Math?
The area of an equilateral triangle in math is the region encompassed or enclosed within the three sides of the equilateral triangle. It is expressed in square units or (unit)^{2}.
What is the Formula of Equilateral Triangle Area?
We can calculate the area of an equilateral triangle given the length of each side. The formula of equilateral triangle area is equal to √3/4 times of square of the side length of the equilateral triangle.
☛ Also Check:
How do you Find the Perimeter and Area of an Equilateral Triangle?
The area of an equilateral triangle is √3/4 × (side)^{2} square units and the perimeter of an equilateral triangle is 3 times a side of the equilateral triangle.
How do you Calculate the Height Using Area of an Equilateral Triangle?
Given the area of an equilateral triangle, we can find the measure of each side using the formula, Area = √3/4 × (side)^{2}. For finding the height of an equilateral triangle from the side length, we use the Pythagoras theorem (hypotenuse^{2 }= base^{2} + height^{2}). So, the formula of height comes as ½ × (√3 × side).
How to Find the Sides of an Equilateral Triangle if the Area of an Equilateral Triangle is known?
If the area of an equilateral triangle is known, we put the given value in the following formula and solve for the length of the side:
Area of equilateral triangle = (√3/4)a^{2 }where a is the length of the side of the equilateral triangle.
What is the Use of the Area of Equilateral Triangle Calculator?
The area of an equilateral triangle calculator is an online tool used to determine the area. This is the quickest mode to calculate the area of an equilateral triangle by providing an input value such as the length of the side. Try Cuemath's area of an equilateral triangle calculator now and calculate the area in a few seconds.
What is the Area of Equilateral Triangle with Side 2 cm?
The area of an equilateral triangle with a side 2 cm is given as Area = √3/4 × (side)^{2}. By substituting the value of side as 2, we get Area = √3/4 × (2)^{2 }= √3 cm^{2}. Therefore, the area of an equilateral triangle with a side length of 2 cm is √3 square centimeters.
How to Find Area of Equilateral Triangle without Height?
When the height of the triangle is not given, then the equilateral triangle area can be calculated using its side length by using the formula Area = √3/4 × (side)^{2} square units.
How to Find Area of Equilateral Triangle with Perimeter?
When the perimeter of an equilateral triangle is known, then we can first find the side of the triangle by dividing the perimeter by 3. Then, we can find the area of the equilateral triangle by using the formula √3/4 × (side)^{2}.
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