The circumference of a circle is the distance around the circle. It is essentially the perimeter of the circle. The formula for calculating the circumference \( C \) of a circle is given by:
\[ C = 2\pi r \]
or
\[ C = \pi d \]
where:
- \( r \) is the radius of the circle (the distance from the center to the edge),
- \( d \) is the diameter of the circle (the distance across the circle through the center, which is twice the radius), and
- \( \pi \) (pi) is a mathematical constant approximately equal to 3.14159.
Using these formulas, you can calculate the circumference if you know either the radius or the diameter of the circle.