Jupiter is a gas giant. It's near the threshold where adding more mass to it makes it smaller, not larger, as the added gravitational pull would make it denser.

Jupiter is a gas giant. It's near the threshold where adding more mass to it makes it smaller, not larger, as the added gravitational pull would make it denser. But what would make it larger is if it was warmer. The radius of a planet like jupiter scales to the 1.6th power of it's temperature. Jupiter is actually slowly shrinking in size as the primordial heat of its formation is radiated away.