Jupiter’s approximate average density is 1.33 grams per cubic centimeter.
This low density reflects Jupiter’s composition and enormous size. The planet is a gas giant made primarily of hydrogen and helium, so its average density is only slightly greater than that of water, despite the immense pressure and exotic forms of matter deep inside.
Jupiter’s measured average density is about 1.326 g/cm³, which is commonly rounded to 1.33 g/cm³ in trivia and educational references. It is lower than the density of every terrestrial planet, including Earth, whose average density is about 5.5 g/cm³.
The figure is an average for the whole planet, not the density of its cloud tops or a solid surface—Jupiter has no sharply defined solid surface. Its mass is about 318 Earth masses, but its volume is roughly 1,321 times Earth’s, which explains why its average density remains relatively modest.