Jupiter’s mass is approximately 318 times the mass of Earth. This comparison is a mass ratio: Jupiter does not contain 318 physical Earths, but its total amount of matter is about 318 Earth masses.
Jupiter is the most massive planet in the Solar System, outweighing all the other planets combined by roughly 2.5 times. Its enormous mass comes mostly from hydrogen and helium, the same light elements that dominate the Sun. Despite its size, Jupiter’s average density is only about 1.33 times that of water, because it is made largely of gases and fluids rather than dense rock.
A common mix-up is confusing mass with diameter or volume. Jupiter is about 11 times wider than Earth and could contain roughly 1,300 Earths by volume, but its mass is about 318 Earth masses. Astronomers also use the term “Jupiter mass” as a standard unit when describing giant exoplanets and brown dwarfs.