A sphere is a perfectly round geometrical object in three-dimensional space... and you can continue this reading at Wikipedia: Sphere. I bet, if you came here looking to find the volume of a sphere, you already know what the sphere is, so I skip the intro.
The formula for the volume of a sphere is
and this is the exact formula used by the calculator below. Just enter the radius and get the volume.
People always ask for the dimension of units. The fact is that formula does not care about dimensions. If it is meters, you get the cubic meters, if it is feet, you get the cubic feet and so on. Use the common sense.
This calculator can also find the radius given the volume. And the formula for the radius is