Using the mean diameters in this collection, Jupiter is about 11 times as wide as Earth. Line up Earth diameters across Jupiter to see what that means as a length.
Why volume feels so different
The spherical-volume ratio is roughly 1,300, because volume grows with the cube of diameter. This is equivalent volume, not a promise that 1,300 rigid Earth-sized spheres would pack inside Jupiter.
Bring the giant down to Earth
With Earth as a 2 cm marble, Jupiter becomes roughly 22 cm across. Try another marble size and imagine the two objects together. The scene uses mean diameters; equatorial values would give a slightly different ratio.