Roblox uses a stud as a distance unit, and one stud is about 0.28 meters, so the Moon would be roughly 13,800,000 studs across if you mean its diameter.

Quick math

  • Moon diameter: about 3,474 km.
  • Convert km to meters: 3,474,000 m.
  • Divide by 0.28 m per stud.
  • Result: about 12.4 to 13.8 million studs, depending on the exact Moon size value used.

What that means

That’s far beyond anything you could reasonably build in Roblox, so a Moon- sized object would be more of a scale reference than a practical in-game model.

Small note

If you meant the Moon’s distance from Earth instead of its size, that would be much bigger still, in the billions of studs.