# 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 |

### 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

### 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.