Circle Calculator

Circle is a two dimensional closed figure which contains set of all points in the plane which are equidistant from a point called center. The straight line which passes through the center of circle and joins two points on a circle is called diameter. Half of the diameter is called radius.

Radius r
Diameter d
Circumference C
Area A
In Terms of Pi π
Circumference C
Area A

Make use of this free Circle Calculator tool to find the unknown parameters like area, circumference and diameter of circle. Enter the inputs in the input section allotted and hit the calculate button to avail results in no time. Check out the simple formulas of circle and step by step procedures to calculate the circle area, circumference in the following sections. We have also given the solved examples for your comfort and understand the topic clearly.

Circle Formulas

The simple and universal formulas to calculate area, circumference and diameter of circle are here

1. Area of Circle Formula:

  • If you know radius,
    • Area A = πr²
  • If you know diameter,
    • Area A = (π/4)d²
  • If you know circumference,
    • Area A = C² / 4π

2. Circumference of Circle Formula:

  • If you know radius,
    • Circumference C = 2πr
  • If you know diameter,
    • Circumference C = πd
  • If you know Area,
    • Circumference C = 2√(πA)

3. Diameter of Circle Formula:

  • If you know radius,
    • Diameter d = r/2
  • If you know Area,
    • Diameter d = (√πA) / 4
  • If you know circumference,
    • Diameter d = C/π

4. Radius of a Circle Formula:

  • If you know diameter,
    • Radius r = 2d
  • If you know Area,
    • Radius r = √(A / π)
  • If you know circumference,
    • Radius r = C/2π

Steps to Calculate Circle Area, Circumference

The required steps to find the area, circumference, diameter and radius of circle are listed here:

Area of Circle:

  • Note down the radius of the circle from the given question.
  • Square the radius.
  • Multiply the result with π constant value.
  • Obtained is the area.

Circle Circumference:

  • Get the circle radius of the question.
  • Double the radius.
  • Multiply it with the obtained output to get the circumference.

Diameter of Circle:

Divide the given diameter by 2 to find the radius of circle.

Example Questions on Circle

Example 1: Find the area of circle having radius 7.8 cm?


Given that,

Radius r = 7.8 cm

Area of Circle Formula is A = πr²

Put these values in above equation

A = π * 7.8 * 78

= 3.14 * 7.8 * 7.8

= 3.14 * 60.84 = 191.03

∴ Area of circle having 7.8 cm radius is 191.03 cm².

Example 2: Find the radius of circle having circumference is 10.6 m?


Given that,

Circumference C = 10.6 m

Radius of Circle r = C/2π

= 10.6/2π = 10.6/(2 * 3.14)

= 10/6.28 = 1.59

∴ Radius of circle is 1.59 m

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FAQs on Circle Calculator

1. How do you calculate the length of a circle?

Length of a circle is called its circumference which is the total distance around the circle. Multiply the diameter of a circle with π to get its circumference.

2. What is the diameter of circle with radius 20 feet?

Radius of circle r = 20 feet

Diameter formula is d = 2r

d = 2 * 20

Circle diameter = 40 feet

3. How can I use Circle Calculator?

Enter the required credentials in the input sections of the calculator and hit on the calculate button to check radius, diameter, circumference and area of circle as output.

4. What is the diameter of the circle?

Diameter is a line that combines two points on the circle and passes through center. Diameter is double the radius.

Circle Calculator

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