12 to 13 inches:  Collar or Youth
Collar necklaces are usually stiff or have multiple strands that  fit snugly around the neck. 

14 to 16 inches:  Choker
A choker necklace sits around the base of the neck or just below.  A classic length that works well with almost any style of clothing neckline

17 to 19 inches:  Princess
A princess length necklace is a popular length & common with pendants. Wear with high necklines or  plunging necklines. 

20 to 24 inches:  Matinee
The matinee length necklace falls flatly on the chest. From turtlenecks to evening gowns, the matinee length is ideal for day or evening. 

28 to 36 inches:  Opera
A versatile, must have in your wardrobe, the opera necklace can also easily transform from day to evening.  It can be worn single, double, or multiple loops. It can even be designed to transform into a bracelet.  Knotting it or adding a decorative clasp can give it yet another look. 

Over 45 inches:  Rope or Lariat
Measuring at least 45 inches long, this versatile piece can be altered for many different looks. Double or triple it up and style accordingly with your wardrobe for dramatic fashion.