Body diameters to scale. Positions and surface artwork are illustrative; Saturn’s rings are excluded.
A change of perspective
2.6432× the diameter. See how the two worlds measure up.
Diameter is a distance across an object. Volume grows with the cube of that distance.
Choose a size to bring this comparison down to Earth.
Callisto: Diameter calculated as twice JPL’s volume-equivalent mean radius: 2 × 2,410.30 km = 4,820.6 km. The listed radius sigma of 1.50 km becomes a diameter sigma of 3.0 km. This describes a sphere with Callisto’s volume, rather than a separate equatorial or polar measurement.
Earth: Twice the source mean radius; body diameter only, excluding rings.
Diameter calculated as twice JPL’s volume-equivalent mean radius: 2 × 2,410.30 km = 4,820.6 km. The listed radius sigma of 1.50 km becomes a diameter sigma of 3.0 km. This describes a sphere with Callisto’s volume, rather than a separate equatorial or polar measurement.
Callisto is a moon of Jupiter. Its mean diameter is approximately 4,821 km, compared with 5,262 km for Ganymede. Dividing their diameters gives about 0.916: if Ganymede were drawn 10 cm wide, Callisto would be about 9.16 cm wide. These figures are calculated from the mean radii in JPL’s satellite physical parameters.
JPL defines mean radius using a sphere of equivalent volume. Doubling Callisto’s listed radius gives 4,820.6 km, with a corresponding sigma of 3.0 km. Equatorial and polar diameters measure specific directions; this value represents overall volume. The scale ratio compares widths, not masses or orbital distances. Artwork is illustrative. See our measurement methodology.