The Moon is .273 times the diameter of Earth. [see page for Earth]
The Moon is 1.09 times the diameter of Triton (a satellite of Neptune).
The Moon is .958 times the diameter of Io (a satellite of Jupiter).
The Moon is 2.16 times the diameter of Titania (a satellite of Uranus).
The Moon is .513 times the diameter of the planet Mars.
The Moon is 3.31 times the diameter of Tethys (a satellite of Saturn).
The Moon is 8.84 times the diameter of Mimas (a satellite of Saturn).
The Moon is 15.8 times the diameter of Phoebe (a satellite of Saturn).
The Moon is .069 times the diameter of the planet Uranus.
The Moon is 39.3 times the diameter of Pandora (a satellite of Saturn).
The Moon is 0.03 times the diameter of the planet Saturn.