The formula to calculate the volume of a sphere is:
\[ V = \frac{4}{3} \pi r^3 \]
In this formula, \( V \) represents the volume, \( \pi \) is a mathematical constant (approximately 3.14159), and \( r \) is the radius of the sphere. The missing part you might be looking for is the term \( r^3 \), which indicates that the volume depends on the cube of the radius.