The area the a circle is the room occupied through the circle in a two-dimensional plane. Alternatively, the room occupied in ~ the boundary/circumference of a one is referred to as the area that the circle. The formula because that the area of a circle is A = πr2, whereby r is the radius the the circle. The unit of area is the square unit, for example, m2, cm2, in2, etc. Area of circle = πr2 or πd2/4 in square units, whereby (Pi) π = 22/7 or 3.14. Pi (π) is the proportion of circumference to diameter of any type of circle. The is a one-of-a-kind mathematical constant.

You are watching: What is the circumference of a circle with a diameter of 18 inches

The area of a circle formula is beneficial for measure the region occupied by a circular ar or a plot. Suppose, if you have a one table, then the area formula will help us come know how much towel is needed to cover the completely. The area formula will also aid us to understand the boundary length i.e., the one of the circle. Does a circle have volume? No, a one doesn't have a volume. A circle is a two-dimensional shape, it does not have volume. A circle only has actually an area and also perimeter/circumference. Let us discover in detail about the area of a circle, surface area, and also its circumference v examples.

1.Circle and Parts of a Circle
2.What Is the Area of Circle?
3.Area of circle Formulas
4.Derivation that Area of a one Formula
5.Surface Area of one Formula
6.Real-World instance on Area the Circle
7.FAQs top top Area of Circle

Circle and Parts that a Circle

A one is a repertoire of point out that room at a addressed distance indigenous the facility of the circle. A circle is a closeup of the door geometric shape. We watch circles in day-to-day life such together a wheel, pizzas, a circular ground, etc. The measure of the room or region enclosed within the circle is well-known as the area of the circle.


Radius: The street from the center to a allude on the border is referred to as the radius that a circle. That is stood for by the letter 'r' or 'R'. Radius plays critical role in the formula for the area and also circumference the a circle, which us will discover later.

Diameter: A line the passes v the center and also its endpoints lied on the one is referred to as the diameter the a circle. It is represented by the letter 'd' or 'D'.

Diameter formula: The diameter formula that a one is twice its radius. Diameter = 2 × Radius

d = 2r or D = 2R

If the diameter the a circle is known, that is radius deserve to be calculation as:

r = d/2 or R = D/2

Circumference: The circumference of the circle is equal to the size of that is boundary. This way that the perimeter that a circle is equal to its circumference. The length of the rope the wraps approximately the circle's boundary perfectly will certainly be same to its circumference. The below-given figure helps girlfriend visualize the same. The circumference deserve to be measured by utilizing the given formula:


where 'r' is the radius of the circle and π is the mathematical continuous whose value is approximated to 3.14 or 22/7. The circumference of a circle deserve to be offered to discover the area of the circle.

For a circle with radius ‘r’ and also circumference ‘C’:

π = Circumference/Diameterπ = C/2r = C/dC = 2πr

Let us know the various parts that a circle making use of the adhering to real-life example.

Consider a circular-shaped park as displayed in the figure below. We deserve to identify the various parts of a circle with the help of the figure and table offered below.


In a CircleIn ours parkNamed by the letter
ChordPlay area entrancePQ
RadiusDistance indigenous the fountain come the enntrance gate gateFA
DiameterStraight line Distance between Entrance Gate and also Exit Gate through the fountainAFB
Minor segmentThe smaller area of the park, i beg your pardon is presented as the beat area
Major segmentThe larger area that the park, other than the pat area
Interior part of the circleThe environment-friendly area the the totality park
Exterior component of the circleThe area outside the border of the park
ArcAny curved part on the circumference.

The area that a one is the lot of room enclosed in ~ the border of a circle. The an ar within the border of the one is the area populated by the circle. The may additionally be described as the total variety of square devices inside that circle.

The area the a circle can be calculated in intermediate steps from the diameter, and also the circumference of a circle. Indigenous the diameter and the circumference, us can discover the radius and also then find the area the a circle. Yet these formulae carry out the shortest method to find the area the a circle. Suppose a circle has a radius 'r' climate the area of circle = πr2 or πd2/4 in square units, wherein π = 22/7 or 3.14, and also d is the diameter.

Area of a circle, A = πr2 square units

Circumference / Perimeter = 2πr units

Area the a circle can be calculation by using the formulas:

Area = π × r2, where 'r' is the radius.Area = (π/4) × d2, whereby 'd' is the diameter.Area = C2/4π, wherein 'C' is the circumference.

Examples making use of Area of circle Formula

Let us think about the following illustrations based upon the area of one formula.

Example1: If the length of the radius the a one is 4 units. Calculation its area.

Solution:Radius(r) = 4 units(given)Using the formula for the circle's area,Area that a one = πr2Put the values,A = π42A =π × 16A = 16π ≈ 50.27

Answer: The area the the circle is 50.27 squared units.

Example 2: The length of the largest chord that a one is 12 units. Uncover the area of the circle.

Solution:Diameter(d) = 12 units(given)Using the formula for the circle's area,Area of a one = (π/4)×d2Put the values,A = (π/4) × 122A = (π/4) × 144A = 36π ≈ 113.1

Answer: The area of the circle is 113.1 square units.

Area of a Circle making use of Diameter

The area of the one formula in regards to the diameter is: Area of a circle = πd2/4. Right here 'd' is the diameter the the circle. The diameter the the circle is double the radius the the circle. D = 2r. Normally from the diameter, we require to first find the radius the the circle and then uncover the area of the circle. Through this formula, we can straight find the area of the circle, native the measure of the diameter of the circle.


Area of a Circle using Circumference

The area of a circle formula in terms of the circumference is offered by the formula (dfrac(Circumference)^24pi). There room two simple steps to uncover the area of a circle native the given circumference of a circle. The circumference of a circle is an initial used to uncover the radius the the circle. This radius is further valuable to find the area of a circle. However in this formulae, we will be able to directly find the area that a circle indigenous the one of the circle.


Area the a Circle-Calculation

The area of the circle deserve to be conveniently calculated either from the radius, diameter, or circumference of the circle. The consistent used in the calculation of the area the a one is pi, and it has actually a fountain numeric worth of 22/7 or a decimal worth of 3.14. Any type of of the worths of pi deserve to be used based upon the requirement and also the need of the equations. The below table mirrors the perform of formulae if we understand the radius, the diameter, or the one of a circle.

Area that a circle when the radius is known.πr2
Area that a circle as soon as the diameter is known.πd2/4
Area the a circle as soon as the circumference is known.C2/

Why is the area of the one is πr2? To understand this, let's first understand exactly how the formula for the area of a one is derived.


Observe the over figure carefully, if we break-up up the circle right into smaller sections and also arrange castle systematically it develops a form of a parallelogram. Once the one is separated into also smaller sectors, it slowly becomes the shape of a rectangle. The an ext the number of sections that has more it tends to have a form of a rectangle as presented above.

The area that a rectangle is = size × breadth

The breadth that a rectangle = radius that a one (r)

When we compare the size of a rectangle and also the circumference of a one we can see the the length is = ½ the one of a circle

Area of circle = Area that rectangle developed = ½ (2πr) × r

Therefore, the area the the one is πr2, whereby r, is the radius that the circle and also the value of π is 22/7 or 3.14.

The surface area that a one is the same as the area of a circle. In fact, as soon as we speak the area the a circle, we average nothing however its total surface area. Surface area is the area populated by the surface of a 3-D shape. The surface of a round will be spherical in shape however a one is a straightforward plane 2-dimensional shape.

If the length of the radius or diameter or also the one of the circle is given, then us can find out the surface ar area. That is stood for in square units. The surface area of circle formula = πr2 wherein 'r' is the radius the the circle and also the value of π is about 3.14 or 22/7.

Ron and also his girlfriend ordered a pizza top top Friday night. Each slice was 15 centimeter in length.

Calculate the area that the pizza that was bespeak by Ron. You deserve to assume that the length of the pizza slice is same to the pizza’s radius.


A pizza is circular in shape. For this reason we have the right to use the area the a circle formula to calculation the area of the pizza.

Radius is 15 cm

Area of one formula = πr2 = 3.14 × 15 × 15 = 706.5

Area the the Pizza = 706.5 sq. Cm.

Example 4: A cable is in the shape of an it is provided triangle. Each side of the triangle measures 7 in. The cable is bent into the form of a circle. Discover the area the the circle that is formed.


Perimeter the the it is provided Triangle: Perimeter the the triangle = 3 × side = 3 × 7 = 21 inches.

Since the perimeter the the it is provided triangle = circumference of the one formed.

Thus, the perimeter that the triangle is 21 inches.

Circumference that a one = 2πr = 2 × 22/7 × r = 21. R = (21 × 7)/(44) = 3.34.

Therefore, the Radius that the circle is 3.34 cm. Area that a circle = πr2 = 22/7 ×(3.34)2 = 35.042 square inches.

Therefore, the area the a one is 35.042 square inches.

Example 5: The time shown in a one clock is 3:00 pm. The size of the minute hand is 21 units. Find the distance traveled by the tip of the minute hand once the time is 3:30 pm.

See more: How Much Is 46 Out Of 48 As A Percentage Calculator: 46 Is What Percent Of 48


When the minute hand is in ~ 3:30 pm, it covers fifty percent of the circle. So, the street traveled through the minute hand is actually half of the circumference. Distance (= pi) (where r is the length of the minute hand). Thus the distance spanned = 22/7 × 21 = 22 × 3 = 66 units. Therefore, the distance traveled is 66 units.