A baby grand piano is classified as such because of its length, which varies from 4 feet 6 inches at the smallest and 5 feet 8 inches at the largest. Most baby grand pianos are 5 feet 1 inch in length and 5 feet wide.
Some companies describe a piano of less than 5 feet in length as a "small" grand piano. The baby grand piano introduced in the 1930s was 5 feet and 1 inch long. This piano is the most popular of the grand pianos, because it maintains the desired aesthetic of the grand piano without taking up too much space.