How to measure your wrist?
1) Take a tape measure or rope and wrap it around your wrist until the two ends touch without sagging.
The size of the wrist should be free from slack and not so tight that it stops blood circulation.
2) Mark the exact length on the rope and use a ruler to determine your true size.
3) Now how to choose a ready-made bracelet of the desired length?
4) Order a bracelet of this size.