What is circumference anyway?
Answer: The circumference of a circle is the edge or rim of a circle itself. It is the equivalent of 'perimeter' for a circle. In other words, if you took a circle and unrolled it, you would have its circumference. You can use either of the formulas below to find the circumference . One formula use the radius of a circle; the other formula uses the diameter.
What is the formula for circumference?
|Formula using Diameter||Formula using Radius|
$$ Circumference = \pi \cdot diameter $$
$$ Circumference = 2\pi\cdot radius $$
**These two formulas are just two different ways of finding the same thing (circumference) because the diameter of a circle =2• radius. So you can use whichever formula is more convenient. If you know a circle's radius, use the first version of the formula; if you know the diameter, use the second
The Circle Song
The rotating line on the left is an example of a circle's radius.
If the radius of a circle is 1 inch (1"), then the circumference of the circle = 2 Π • 1" ≈ 6.28 "