From largest to smallest, a list of the planets ranked by size is Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars and Mercury. The size of the planets can be compared by calculating the radius, diameter, circumference or volume.
The largest planet, Jupiter, is 1,120 percent the size of the Earth, with a radius of 43,441 miles compared to the Earth's radius of 3,959 miles. Saturn is 945 percent larger than Earth and has a radius of 36,184 miles. Uranus has a radius of 15,759 miles, Neptune has a radius of 15,299 miles, Venus has a radius of 3,761 miles, Mars has a radius of 2,460 miles and Mercury has a radius of 1,516 miles.