30cm or 12-13 inches: Worn tight around the neck.
32cm or 14-16 inches: Choker - Falls just above the collarbone.
42cm or 17-19 inches: Princess - A popular, medium length.
50cm or 20-24 inches: Matinee - A popular longer style.
70cm or 28-34 inches: Opera - Noticeably long and can usually be worn single strand or doubled.
120cm+ or 48+ inches: Rope and Lariat - A wrap-around style without a regular clasp.