how big is the moon compared to the earth The Moon, Earth's natural satellite, is significantly smaller compared to our planet. With a diameter of approximately 3,474 kilometers (2,159 miles), the Moon is about 27% the size of Earth. In terms of mass, the Moon is around 1.2% of Earth's mass. Its smaller size contributes to its gravitational pull, which is about 1/6th the gravity experienced on Earth's surface.