What's the radius of the planets in Sins? (for XSI)

I want to make a new building that goes around the planet but I don't know the radius of planets so, what is the exact radius of the planets in sins (with decimals and all that).  If you still don't understand what I mean I'll explain further.  When you create a sphere in XSI you can edit it.  One of the options is radius, what is the number that I should put there to make my sphere the exact same size of a planet in Sins.

1. What's the radius of a planet
2. What's the radius of a gas gaint sized planet
3. What's the radius of a star

If anyone knows please let me know as I can't import meshes into sins and I can't get 3dsmax so...