The circumference of a circle can be calculated using the following formula:

$C = 2 \pi r$

Where:

• $C$ is the circumference,
• $r$ is the radius of the circle, and
• $\pi$ is a constant approximately equal to 3.14159.

Alternatively, if you know the diameter ($d$) of the circle, the formula becomes:

$C = \pi d$

Would you like a detailed example, or do you have any specific questions about this?

Here are 5 related questions:

1. How do you find the radius if the circumference is given?
2. What is the relationship between the diameter and the radius of a circle?
3. How does the area of a circle relate to its circumference?
4. What is the value of $\pi$, and why is it important in circle calculations?
5. Can the circumference formula be applied to ellipses or other shapes?

Tip: Always remember that the diameter of a circle is twice its radius, so knowing one helps in finding the other.