What is the equation for circumference?

Answer 1

Circumference is the specific term for the length of the perimeter of a circle. The perimeter of a circle is the circumference, and to find it, we need to know the radius or diameter of the circle. (As the diameter of a circle equals twice the radius of the circle, knowing one will mean we can know the other.) If we compare circles, we will find that all circles, regardless of their size, have something in common. The something is that all circles have in common is that the ratio between the diameter of any circle and its circumference is a constant. It's always the same for any size circle. And it's an irrational number we call pi. You've heard that, and that's what it is - a ratio. It's equal to about 3.14159 or so. (We know pi is an irrational number.) To find the circumference (c) of any circle, multiply pi (π) times its diameter (d). Or, multiply 2 times its radius (r) times pi (π). Same thing. Here are the two "versions" of the formula. c = π x d or c = 2 x π x r c equals pi times d or c equals two times pi times r. A link is provided to the Wikipedia article on circumference.