The size of a grapefruit can vary depending on the type and variety of the fruit. On average, a grapefruit is about the size of a softball or around 10 cm (4 inches) in diameter. However, some types of grapefruit can be larger or smaller than this average size. For example, the Oro Blanco grapefruit can be as large as a small melon, while the Star Ruby grapefruit is usually smaller than the average size. The weight of a grapefruit can also vary depending on its size and type, ranging from around 140 grams (5 ounces) to 450 grams (1 pound) or more.