Necklaces are fine accents to clothing and every girl surely has one in their jewelries. These pieces vary in length, suggesting different clothing for different occasions.
To accurately measure where each necklace will drape on your neck, Palamuti by PJ Valenciano suggests to try wrapping a ribbon around your neck to find your desired length, and then measure it end to end against a ruler, yardstick, or a measuring tape.
Now here are the seven categories of necklace length:
Collar (12"-13")
This type is very suitable for formal occasions, best with a strapless ensemble but can also be paired with boat necks, V-necks and off-the-shoulder tops. It’s quite a snug but very sophisticated if you manage to pull this off. One should have a thin neck as this is worn tight and high up on the neck.
Choker (14"-16")
This is less snug than the collar type and is ideal for females with thicker necks as it falls just above the collar bone. You can show off your love long neck with this type.
Princess (17”-19”)
The most popular length, worn just below the collar bone. It is perfect for pendants and it works well with clothes with either low or high necklines, but best not to let the clothing and the jewelry meet at the same spot.
Matinee (20”-24”)
A good choice for office, casual, formal, or business occasions. This length drapes over the breast bone.
Opera (28”-34”)
This can be worn in many ways and is very elegant as it draws attention away from the neck. Can be worn with double loop for a more dramatic effect.
Source:
http://www.delamina.com/content/tips-info-links/jewelry-basics/necklace-lengths/