What is the Formula for area of a circle?


When it comes to find the area of a circle, there is a nice formula to do the task. Once kids know the formula for area of a circle then they can do most of the problems related to circles.


In this post we will talk about the formula to find the area of any circle. The key parameters to find the area of a circle are its radius and the constant “pi”. You can easily find the area when the radius of the circle is given.  Remember, the value of constant ”pi ()” is always equal to 3.14 rounded to two decimal places, (some countries use p = 22/7).


Formula For Area Of A Circle Using Its Radius


Recall the area of a circle basics lesson, radius is the fixed distance between the center of the circle to any point on the circle. Most often letter “r” is used to represent the radius of a given circle. The next thing is needed to in the formula for area of a circle is the constant Pi ( )= 3.14


how to find the area of a circleuse of pi in formula for area of a circle


In other words, we can say that the area = pi x radius x radius.


For example; consider a circle with radius = 2 cm. then we can find its area by substituting r = 2 and pi = 3.14 as shown below;


How to use formula to find the area of a circle

Similarly area of any other circle with any radius can be calculated by changing the value of radius “r”. We used the simplest value of radius “r” for explanation purposes.


Formula for Area of a Circle using its diameter


When the given is the diameter of the circle instead its radius, student can modify the formula for area of a circle. The letter “d” is used to represent the diameter of a circle. Below is the formula to find the area of a circle using its diameter “d”.



or we can write it as = pi x diameter x diameter 4


Recall, diameter =  2 x radius of the circle, or in other words; radius = diameter/2. You can divide the diameter by “2? to get the radius and use the first formula.


We always suggest to stick to only one formula for area of a circle which is one uses radius. When you are given with the diameter of the circle, just divide that value by 2 to get radius and use the first formula to find the area of the given circle.


Area of a circle formula


Hence the formula for area of a circle. Note that the best method to use this formula is using radius in it.




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