Earth’s moon is the brightest object in our night sky. It appears quite large, but that is only because it is the closest celestial body. The moon is a bit more than one-fourth (27 percent) the size of Earth, a much smaller ratio (1:4) than any other planets and their moons. Earth’s moon is the fifth largest moon in the solar system.
The moon’s mean radius is 1,079.6 miles (1,737.5 kilometers). Double those figures to get its diameter: 2,159.2 miles (3,475 km), less than a third the width of Earth. The moon’s equatorial circumference is 6,783.5 miles (10,917 km).