# Circle Circumference Calculators

Each our сircumference сalculator is solving several problems of practical geometry. Here are some of them: to calculate circumference, circumference to diameter, diameter to circumference, find circumference, circumference to radius, calculate diameter from circumference, radius to circumference, calculate circumference from diameter, calculate the circumference of a circle, circumference from diameter, etc.

Note: For your convenience the circumference calculators perform calculations in both directions. You can also select units of measure for both input data and results.

## Radius to Circumference & Circumference to Radius Calculator

r

C

#### Theory

You are given the radius of a circle. Find the circumference.
The circumference C of a circle of radius r is given by the formula: C = 2πr
So, the circumference is equal to double product of radius by π. π(Pi) is a mathematical constant approximately equal to 3.14

You are given the circumference of a circle. Find the radius.
Let us change the formula of circumference C = 2πr so that r (radius) is alone on one side of the equation. So, we get the formula for finding the radius r of a circle of circumference C: r = C/(2π)

## Diameter to Circumference & Circumference to Diameter Calculator

d

C

#### Theory

You are given the diameter of a circle. Find the circumference.
Diameter d of a circle is a straight line connecting two points of a circle and passing through the center. Diameter of a circle measures twice the radius: d = 2r
The circumference C of a circle of diameter d is given by the formula: C = 2πr = πd
So, the circumference is equal to the product of diameter by π.

You are given the circumference of a circle. Find the diameter.
Let us change the formula of circumference C = πd so that d (diameter) is alone on one side of the equation. So, we get the formula for finding the diameter d of a circle of circumference C: d = C/π

## Area to Circumference & Circumference to Area Calculator

A

C

#### Theory

You are given the area of a circle. Find the circumference.
Area of a circle with radius r is given by the formula A = πr2.
Then the circumference C of a circle of area A is given by the formula: C = 2√(πA)
So, the circumference C is equal to the double square root of π multiplied by area A. π (Pi) is a mathematical constant approximately equal to 3.14

You are given the circumference of a circle. Find the area.
Let us change the formula of circumference C = 2√(πA) so that A (area) is alone on one side of the equation. So, we get the formula for finding the area A of a circle with circumference C: A = C2/(4π)
The area A is equal to C squared divided by the product of π by 4.

## Circle Inscribed in a Square Calculator

a

C

#### Theory

A circle is inscribed in a square. You are given the side length of the square. Find the circumference of the circle.
When a circle is inscribed in a square, the diameter d of the circle is equal to the side length a of the square, i.e. d=a. The circumference C of a circle inscribed in a square with side length a is given by the formula: C = πd = πa

A circle is inscribed in a square. You are given the circumference. Find the side length of the square.
Let us change the formula of circumference C = πa so that a (side length of the square) is alone on one side of the equation. So, we get the formula for finding the side length of the square containing described circle with circumference C: a = C/π