Area of a Circle Calculator

To use area of a circle calculator, choose what you have from radius or diameter, Enter its value, choose the unit, and click Calculate


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Area of a Circle Calculator  

Use the area of a circle calculator to find the area of any circular region with both radius and diameter. It also calculates the radius if you enter diameter and vice versa. 

What is the area of the circle?

The area of a circle is a measure of the space contained within its boundary. The formula to find the area A of a circle, given its radius r, is:

A = πr^2 


  • A is the area of the circle. 
  • π (pi) is a mathematical constant approximately equal to 3.14159, though it can be simplified to 22/7 for some calculations.
  • r is the radius of the circle, which is the distance from its center to any point on its circumference.

The radius is half the diameter of the circle. If you know the diameter d, you can find the radius using r = d/2.

The formula A = πr^2 derives from the mathematical definition of π as the ratio of a circle's circumference to its diameter. 

Utilizing calculus, the area formula can be proven by summing an infinite series of concentric, infinitesimally thin rings from the circle's center to its outer edge.


Let's calculate the area of a circle with a radius of 7 cm.

A = πr^2

A = π(7cm)^2

A = 3.14159×49cm^2

A ≈ 153.94cm^2

This means that a circle with a radius of 7 cm has an area of approximately 153.94 square centimeters.

The area is always expressed in square units (e.g., square meters, square centimeters, etc.). π is an irrational number, meaning it has no exact decimal representation and no repeating pattern of digits.

Applications of the area of the circle:

The concept of the area of a circle, finds applications in various fields, providing crucial insights and aiding problem-solving and design in numerous contexts:

1. Engineering:

  • Design: Engineers utilize the area of a circle in designing cylinders, pipes, tanks, and gears, among other circular objects.
  • Material Estimation: It helps to estimate the material needed to manufacture circular objects or components.

2. Architecture:

  • Space Utilization: Architects employ the area formula in determining the space usage of circular structures, such as domes or cylindrical towers.
  • Floor Planning: In planning circular spaces or structures within a building to ensure optimal use of space.

3. Mathematics and Computational Geometry:

  • Problem Solving: The area of a circle is pivotal in various geometrical problems and theorems.
  • Algorithm Development: Utilized in developing algorithms related to circular shapes in computational geometry.

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