Planets are generally smaller than stars in terms of size. For example, the largest planets in our solar system, like Jupiter, have diameters of about 86,881 miles (139,822 kilometers), while even the smallest stars, like red dwarfs, can have diameters around 6,000 miles (9,600 kilometers) or more.
In general, stars are massive celestial bodies that produce their own light and heat through nuclear fusion, while planets do not produce light and typically orbit stars.