Welcome to Circle.org - The best Information and reference guide for circle and hteir formulas.

Quick Access circles formulas:

Circumference = 2 • π • radius = π • diameter

Circle Area = π • r² = ¼ • π • d²

Sphere Surface Area = 4 • π • r² = π • d²

Sphere Volume = 4/3 • π • r³ = ( π •d³)/6

Surface Area = (2 • π • r²) + (2 • π • r • height)

Where (2 • π • r²) is the surface area of the "ends" and (2 • π • r • height) is the lateral area (the area of the "side").

Volume = π • r² • height = ¼ • π • d² • height

arc: a curved line that is part of the circumference of a circle

chord: a line segment within a circle that touches 2 points on the circle.

circumference: the distance around the circle.

diameter: the longest distance from one end of a circle to the other.

origin: the center of the circle

pi (): A number, 3.141592..., equal to (the circumference) / (the diameter) of any circle.

radius: distance from center of circle to any point on it.

sector: is like a slice of pie (a circle wedge).

tangent of circle: a line perpendicular to the radius that touches ONLY one point on the circle.

If you're tired of math and want to take a break, we recommend checking out the official website for ebook reader news and information. It has great articles!