Standard Necklace Sizes for Men

45cm (about 18″) – Base of the neck (*for smaller neck sizes)
50cm (about 20″) – to collarbone (*most common length for average men)
60cm (about 24″) – A few inches below the collarbone
70cm (about 28″) – Just at or above the sternum
80cm (about 32″) – Just above the sternum