Both verticals and grands come in a wide variety of sizes. The important thing to know here is that size is directly related to musical quality. Although many other factors also contribute to tonal quality, all else being equal, the longer strings of larger pianos, especially in the bass and mid-range sections, give off a deeper, truer, more consonant tonal quality than the strings of smaller pianos. The treble and bass blend better and the result is more pleasing to the ear. Also, longer grands usually have longer keys that generally allow superior control of musical expression than shorter grands. Therefore, it's best to buy the largest piano you can afford and have space for. Small differences in size between models are more significant in smaller pianos than in larger ones. However, a difference in size of only an inch or two is generally irrelevant, as it could be merely due to a larger cabinet or case.
Vertical pianos are measured from the floor to the top of the piano. Verticals less than 40" tall are known as spinets. They were very popular in the post–World War II period, but in recent years have nearly died out. Verticals from 40" to about 43" or 44" are called consoles. Spinet and console actions must be compromised somewhat in size or placement within the piano to fit them into pianos of this size. The tone is also compromised by the shorter strings and smaller soundboard. For this reason, manufacturers concentrate on the furniture component of spinets and consoles and make them in a variety of decorator styles. They are suitable for buyers whose piano needs are casual, or for beginning students, and for those who simply want a nice-looking piece of furniture in the home. Once students progress to an intermediate or advanced stage, they are likely to need a larger instrument.
Studio pianos, from about 44" to 47", are more serious instruments. They are called studios because they are commonly found in the practice rooms of music schools. Manufacturers make them in both attractive furniture styles for the home and in functional, durable, but aesthetically bland styles for school and other institutional use. If you don't require attractive furniture, you may save money by buying the school style. In fact, many buyers prefer the simple lines of the institutional models.
Verticals about 48" and taller, called uprights, are the best musically. New ones top out at about 52", but in the early part of the 20th century they were made even taller. The tallest verticals take up no more floor space than the shortest ones, but some buyers may find the taller models too massive for their taste. Most uprights are made in an attractive, black, traditional or institutional style, but are also available with exotic veneers, inlays, and other touches of elegance.
The width of a vertical piano is usually a little under five feet and the depth around two feet; however, these dimensions are not significantly related to musical quality.
Grand pianos are measured with the lid closed from the very front of the piano (keyboard end) to the very back (the tail). Lengths start at 4' 6" and go to over 10' (even longer in some experimental models). Widths are usually around 5' and heights around 3', but only the length has a bearing on musical quality.
Grands less than 5' long are the musical equivalent of spinets and consoles; that is, they are musically compromised and are mainly sold as pieces of furniture. Grands between about 5' and 5½' are very popular. Although slightly compromised, they can reasonably serve both musical and furniture functions and are available in many furniture styles. (By the way, piano professionals prefer the term small grand to baby grand. Although there is no exact definition, a small grand is generally one less than about 5½' long.) Above 5½', pianos rapidly improve, becoming professional quality at about 6'. Pianos intended for the home or serious professional top out at about 7' or 7½'. These sizes may also satisfy the needs of smaller concert venues. Larger venues require concert grands, usually about 9' long.