Jupiter and Saturn dominate the outer solar system as the two largest planets and premier examples of gas giants. While both are colossal spheres of hydrogen and helium, a direct comparison reveals a significant disparity in their dimensions and overall bulk. This difference influences their internal structure, composition, and gravitational effect on the surrounding space. To truly understand how big Jupiter is compared to Saturn requires examining the quantitative metrics of their physical size and mass.
Physical Dimensions: Diameter and Volume
The equatorial diameter is the most direct measure of size. Jupiter’s diameter stretches approximately 142,984 kilometers, making it the largest planet by a considerable margin. Saturn, the second largest, follows with an equatorial diameter of about 120,536 kilometers. This difference means that Jupiter is about 1.18 times wider than its ringed counterpart.
The difference in volume is much more pronounced than the linear diameter suggests. Because volume scales with the cube of the radius, a small increase in width results in a massive increase in interior space. Jupiter’s volume is so vast that approximately 1,321 Earths could fit inside it, compared to Saturn’s interior which could contain about 766 Earths.
When comparing the two gas giants directly, Jupiter is capacious enough to hold roughly 1.73 Saturns within its volume. This volumetric ratio illustrates that Jupiter’s internal space is nearly double that of Saturn’s. Although Saturn appears similarly large in images due to its immense ring system, its physical globe is significantly smaller.
Mass and Gravitational Power
The most profound difference between the two planets lies in their total mass, which dictates their gravitational influence. Jupiter is substantially more massive, holding a mass equivalent to about 318 Earths. Saturn is far less substantial, possessing a mass of only about 95 times that of Earth. This means Jupiter is approximately 3.4 times more massive than Saturn.
This massive disparity explains a common point of confusion: why Jupiter is only slightly larger than Saturn despite being over three times as heavy. The answer lies in density and gravitational compression. Both planets are composed primarily of the lightweight elements hydrogen and helium, but Jupiter’s greater mass creates a far more intense gravitational field.
This stronger gravity acts to compress the gas and liquid layers deep within Jupiter’s interior to a much greater degree than Saturn’s gravity does. Jupiter has an average density of approximately 1.3 grams per cubic centimeter, which is slightly denser than water. Saturn, by comparison, is the least dense planet in the solar system, with an average density of only about 0.69 grams per cubic centimeter. This low density means Saturn would famously float if placed in a large enough body of water, while Jupiter would sink.
Visualizing the Difference in Scale
To grasp the magnitude of these differences, one can contextualize the scale with familiar objects. Based on their equatorial diameters, Jupiter is about 11 times wider than Earth, while Saturn is about nine times wider. If Jupiter were scaled down to the size of a basketball, Saturn would be comparable to a soccer ball, showing a visible but not overwhelming size difference.
The sheer mass of Jupiter is what truly sets it apart from Saturn and all other planets. Jupiter is so massive that it contains more than two times the mass of all the other planets in the solar system combined. This gravitational dominance means Jupiter significantly influences the orbits of comets and asteroids passing through the solar system.
Even Saturn’s substantial mass is dwarfed by this fact, emphasizing that while Saturn is the solar system’s second giant, Jupiter’s scale is unique. The comparison ultimately shows that Jupiter is not merely bigger than Saturn; it is fundamentally more massive and gravitationally dominant, existing in a class of its own among the planets.