Sorry, I am confusing them.
Spherical Volume is 4/3 * PI * radius cubed
Spherical Surface is 4 * PI * radius squared
Diameter of:
Io - 1942 miles
Europa - 2000 miles
Ganymede - 3400 miles
Callisto - 3000 miles
Earth - 7926 miles
The Jovian moons are bigger than I recalled. The Earth has 5 times the surface of Ganymede, the largest, and 13 times the volume.
Io would make an excellent ranch for me. 1/5 the surface area is pretty awesome. I love the solar system. I wish I was 10, I'd have a chance to have a real ranch. Thanks for the formulas. You are a gentleman and a scholar.