The nine planets in the solar system range in size from approximately 3,000 to 140,000 kilometers in diameter. Ranked from smallest to largest the planets are Pluto, Mercury, Mars, Venus, Earth, Neptune, Uranus, Saturn and Jupiter.
The farthest planet from the sun is also the smallest. Pluto's diameter is approximately 3,000 kilometers. Little is known about this planet as it is the only one a space probe hasn't visited. Mercury is about 5,000 kilometers in diameter. It is the closest planet to the sun and is very hot because of the sun's close proximity. Mars is called the red planet because of the abundance of rusty iron on its surface. It is the third smallest planet with a diameter of approximately 7,000 kilometers. Venus is the closest planet to Earth in size with a diameter of 12,000 kilometers. Venus is unusual because it rotates in the opposite direction to the other planets. Earth has a diameter of 12,800 kilometers. It is the third planet from the sun and takes 365 days to complete an orbit. Neptune is one of the four gas giants in the solar system. This gaseous ball has a diameter of 50,000 kilometers. Another gas giant, Uranus is 52,000 kilometers wide. Its atmosphere is mostly hydrogen. Saturn is the second largest planet with a diameter of 120,000 kilometers. Second only to Jupiter in size, Saturn is known for its rings. Jupiter is the largest planet with a diameter of 140,000 kilometers. It is larger than 1,000 Earths combined.