To measure your wrist accurately, wrap a sewing tape measure (or string, or a thin piece of paper) around your wrist, just below the prominent bone, and mark where the string meets. Measure the length on a ruler in centimeters, starting from the zero point.

And this is a table of recommended sizes for bracelets, usually the average size of women's bracelets is about 17 cm, men's - about 19 cm.