There is no simple answer to the question of how long a necklace should or must be. The right length depends, among other things, on the time of year and the clothes you are wearing at the time. If you are wearing a sleeveless dress, you will need a necklace of a different length from if you are wearing a roll neck jumper. You can also use a necklace to make yourself look even more feminine, for example by combining it with a low-cut neckline. A choker makes your neck seem a little more delicate.