The common violas sizes are 17, 16.5, 16, 15.5, 15, 14, 13, and 12. Viola sizes are based on the length, in inches, from the end of the viola to the shoulder, or point where the neck emerges from the body of this string instrument. There are some more experimental, larger viola sizes of 18 and 19, but these violas are usually designed for a specific piece of music and are so cumbersome to play that they would not be used every day. Large adults use a viola size of 17, average adults use viola sizes 16.5, 16 or 15, teenagers use viola sizes 15 and 14, and children use viola sizes 13 and 12. To provide comfort while playing and to allow for proper skill development, it is important to fit a viola comfortably to the musician.
Instruments in the violin family vary in size to accommodate different size musicians. Violas come in eight different sizes and range in overall length from 27 inches (68 cm) to 20.5 inches (52 cm). The size of the viola determines the sound of the instrument.
The smaller violas sizes of 12 and 13 do not house enough air space within their body cavities to produce a typical and robust viola sound, but are easier to play and master. These violas often sound fine when played on their own in a solo situation. In a string quartet or even orchestra, however, where the viola is meant to be tuned lower than the violin, smaller violas may fall slightly short of the standard viola sound quality.
On the other hand, larger violas which do produce a heartier sound are usually difficult to play, especially for a beginner. A fairly well-developed skill level is needed to manipulate the longer body of a larger, better sounding viola. Sometimes, musicians tackling these larger sizes for long practice sessions develop injuries. In the end, selecting the proper viola size becomes a balance between sound, comfort, skill level, and even safety.
Selecting the proper size viola should be done with the student’s music teacher or an experienced luthier, a person who makes stringed instruments. This person will either measure the student’s arm from shoulder to wrist, or he will place violas of varying sizes on the student’s left arm and ask her to see if she can wrap her hand around the scroll of the viola. The student will then be asked to play the viola for a short time to determine if she is able to comfortably play the instrument and stay in tune. Finally, once the instrument has been deemed the correct size, the student will need to judge whether the sound quality suits her.