The size of Jupiter is approximately the geometric mean of the sizes of Sun and Earth.
In terms of radii,
The ratio on the left equals 9.95 and the ratio on the left equals 10.98.
The subscripts are the astronomical symbols for the Sun (☉, U+2609), Jupiter (♃, U+2643), and Earth (, U+1F728). I produced them in LaTeX using the mathabx package and the commands \Sun, Jupiter, and Earth.
The mathabx symbol for Jupiter is a little unusual. It looks italicized, but that’s not because the symbol is being used in math mode. Notice that the vertical bar in the symbol for Earth is vertical, i.e. not italicized.