How to find the area of a circle

How to find the area of a circle

The area of a circle is pi times the radius squared (A = π r²).

What is a Circle?

A circle closed aircraft geometric shape. In technical terms, a circle is a locus of a factor shifting around a set factor at a hard and fast distance away from the factor. essentially, a circle is a closed curve with its outer line equidistant from the center. The constant distance from the point is the radius of the circle. In actual lifestyles, you'll get many examples of the circle together with a wheel, pizzas, a circular ground, and so on. Now allow us to analyze, what are the phrases used inside the case of a circle.

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The radius of the circle is the road that joins the middle of the circle to the outer boundary. it is also represented by means of ‘r’ or ‘R’. inside the system for the area and circumference of a circle, radius performs a critical role which you'll research later.


The diameter of the circle is the road that divides the circle into two identical elements. In an easy way we can say, it is simply the double of the radius of the circle and is represented with the aid of’d’ or ‘D’. therefore,

d = 2r or D = 2R


If the diameter of the circle is thought to us, we are able to calculate the radius of the circle, along with;

r = d/2 or R = D/2


Region of Circle


Any geometrical form has its very own vicinity. This area is the location occupied by the shape in a -dimensional plane. Now we can study the place of the circle. So the vicinity included with the aid of one entire cycle of the radius of the circle on a -dimensional plane is the region of that circle. Now how can we calculate the area for any round item or area? In this example, we use the formula for the circle’s vicinity. allow us to talk about the components now.

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region of a Circle system

let us take a circle with radius r.


Area of a circle

in the above determine, we are able to see a circle, wherein radius r from the center ‘o’ to the boundary of the circle. Then the region for this circle, A, is the same to the product of pi and the rectangular of the radius. it's far given with the aid of. The formula for calculating the area of a circle is A = π​r​2 where pi (π) equals 3.14 and the radius (​r​) is half the diameter.


place of a Circle, A = πr2 rectangular units

right here, the value of pi, π = 22/7 or three.14, and r is the radius.

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Derivation of the region of Circle

The region of a circle can be visualized & proved the usage of two strategies, particularly

determining the circle’s location the use of rectangles

figuring out the circle’s place the usage of triangles

let us understand both the strategies separately-

the usage of regions of Rectangles

The circle is divided into sixteen same sectors, and the sectors are arranged as shown in fig. three. The region of the circle can be equal to that of the parallelogram-fashioned parent shaped through the sectors reduce out from the circle. since the sectors have an equal location, every region may have an equal arc length. The pink-colored sectors will make contributions to half of the circumference, and blue-colored sectors will make a contribution to the opposite half. If the range of sectors reduces from the circle is improved, the parallelogram will in the end appear to be a rectangle with a duration same as πr and breadth identical to r.


Area of a Circle the usage of Rectangle

The area of a rectangle (A) may also be the vicinity of a circle. So, we've

A = πr×r

A = πr2

man standing on hill during full moonThe use of regions of Triangles

Fill the circle with radius r with concentric circles. After cutting the circle alongside the indicated line in fig. 4 and spreading the lines, the end result might be a triangle. the bottom of the triangle may be equal to the circumference of the circle, and its height may be equal to the radius of the circle.


region of a Circle using Triangles


So, the location of the triangle (A) can be equal to the area of the circle. we've


A = half×base×height


A = 1/2×(2πr)×r


A = πr2


floor location of Circle formulation

A circle is not anything however the 2-D illustration of a sphere. the full vicinity this is taken within the boundary of the circle is the floor place of the circle. when we are saying we need the area of the circle, then we mean the surface vicinity of the circle itself. every so often, the quantity of a circle additionally defines the area of a circle.


when the duration of the radius or diameter or even the circumference of the circle is already given, then we are able to use the surface components to discover the floor region. The floor is represented in square gadgets.


The floor area of the circle = A = π x r2

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Circumference of Circle

A fringe of closed figures is described as the length of its boundary. when it comes to circles, the fringe is given in a distinct name. it's miles referred to as the “Circumference” of the circle. This circumference is the length of the boundary of the circle. If we open the circle to shape a direct line, then the duration of the straight line is the circumference. To define the circumference of the circle, the know-how of a term called ‘pi’ is required. don't forget the circle shown within the fig. 1, with centre at O and radius r.


Circumference of circle


the fringe of the circle is the same to the length of its boundary. The period of rope which wraps around its boundary flawlessly may be the same to its circumference, which can be measured by the use of the formulation:


Circumference / Perimeter = 2πr gadgets


where r is the radius of the circle.

π, examine as ‘pi’ is described because of the ratio of the circumference of a circle to its diameter. This ratio is the identical for each circle. consider a circle with radius ‘r’ and circumference ‘C’. For this circle


π = Circumference/Diameter

π = C/2r

C = 2πr

The equal is proven in fig. 2.


perimeter of circle

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Calculation of Area of the Circle.

As we recognize, the vicinity of the circle is identical to pi times rectangular of its radius, i.e. π x r2. To locate the place of the circle we need to know the radius or diameter of the circle.


as an example, if the radius of circle is 7cm, then its vicinity could be:


region of circle with 7 cm radius = πr2 = π(7)2 = 22/7 x 7 x 7 = 22 x 7 = 154 sq.cm.


additionally, if we recognize the circumference of the circle, then we will locate the place of the circle.




for the reason that, the circumference is two instances of fabricated from pi and radius of circle, along with:


C = 2πr


consequently, here we can discover the fee of radius,


r = C/2π


once, we've evaluated the fee of radius, we are able to easily discover the place.


rectangular place and Circle place

The location of a circle is expected to be 80% of the region of the rectangular while the diameter of the circle and period of the side of the square is the same.


students can also do an interest by using placing a circular object into a square shape with the equal diameter and facet period, respectively.

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If the region of the rectangular is 100 sq. unit, then the area of the circle may be approximately 80 sq. unit of it.


Solved Examples

We've got mentioned until now approximately the exclusive parameters of the circle inclusive of place, perimeter or circumference, radius, and diameter. allow us to remedy some troubles based on those formulation to understand the concept of vicinity and perimeter in a better manner.


example 1:


what's the radius of the circle whose surface vicinity is 314.159 sq. cm?




by means of the formula of the surface area of the circle, we understand;

A = π x r2

Now, substituting the price:

314.159 = π x r2

314.159 = 3.14 x r2

r2 = 314.159/3.14

r2 = a hundred.05

r = √one hundred.05

r = 10 cm

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example 2:


What are the circumference and the vicinity of the circle if the radius is 7 cm?


Given: Radius, r = 7 cm

We realize that the circumference/ perimeter of the circle is 2πr cm.

Now, substitute the radius value, we get

C = 2 × (22/7)× 7

C = 2×22

C = forty four cm

hence, the circumference of the circle is forty-four cm.

Now, the area of the circle is πr2 cm2

A = (22/7) × 7 × 7

A = 22 × 7

A = 154 cm2


often asked questions about the usage of the location of Circle formulation

a way to calculate the place of a circle?

The region of the circle may be calculated with the aid of the usage of the formulation:


location = π x r2, in terms of radius ‘r’.


vicinity = (π/four) x d2, in phrases of diameter, ‘d’.


region = C2/fourπ, in phrases of circumference, ‘C’.


what is the circumference of a circle?

The fringe of the circle is nothing but the circumference, which is equal to twice of made of pi (π) and the radius of circle, i.e., 2πr.


If the radius of a circle is 15cm. Then locate its vicinity.


Given, radius of circle = 15cm

The vicinity could be;

A = πr2

A = π.152

A = 706.five sq.cm.

If the diameter of a circle is 10cm. Then discover its region.


Given, diameter = 10cm

So, radius might be = 10/2 = 5cm

for this reason, place A = πr2

A = π.52

A= seventy eight.5 sq.cm

If the circumference of a given circle is 30cm. Then what is going to be its vicinity?


Given, the circumference of a circle = 30cm

We recognize, from the formula of circumference, C =2πr

So, we will write,

2πr = 30

or r = 30/2π = 15/π

As we located the cost of r, now we will find the vicinity;


A = πr2

A = π(15/π)2

On fixing we get,

A = seventy one.65 sq.cm.

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