The largest planet in the Solar System is Jupiter. It has a diameter of about 142,984 kilometers (88,846 miles) and a mass of about 318 times that of Earth. Jupiter is a gas giant, composed mostly of hydrogen and helium.

The smallest planet in the Solar System is Mercury. It has a diameter of about 4,879 kilometers (3,031 miles) and a mass of about 0.055 times that of Earth. Mercury is a terrestrial planet, composed mostly of rock and metal.