The formula for the circumference $C$ of a circle when given the diameter $d$ is:

$C = \pi \times d$

If you provide the diameter, I can calculate the circumference for you. Otherwise, if you want to do it yourself, just multiply the diameter by $\pi$ (approximately 3.14159).

Would you like to provide the diameter, or should I explain further?

Related Questions:

1. How do you calculate the area of a circle using the radius?
2. What is the relationship between radius and diameter?
3. How does the circumference change if the diameter is doubled?
4. Can you calculate the circumference if only the radius is given?
5. What are some real-world applications of circle circumference calculations?

Tip: Always remember, the diameter is twice the radius!