Sizes
Children learning the violin often use "fractional-sized" violins: 3/4, 1/2, 1/4, 1/8, 1/10, 1/16, and sometimes even 1/32 sized instruments are used. These numbers do not represent numerically accurate size relationships, i.e., a "1/2 size" violin is not actually half the length of a full-sized violin.
The body length (not including the neck) of a 'full-size' or 4/4 violin is about 14 inches (or smaller in some models of the 17th century). A 3/4 violin is 13 inches, and a 1/2 size is 12 inches. Rarely, one finds a size referred to as 7/8 which is approximately 13.5 inches, sometimes called a "ladies' fiddle." Viola size is specified as body length in inches rather than fractional sizes. A 'full-size' viola averages 16 inches, but may range as long as 18 or 20 inches. Such extremely long instruments may be humorously referred to as "chin cellos."
Read more about this topic: Violin Construction And Mechanics