It is very simple.
it is necessary to measure:
- wrist at the narrowest point
- the brush at the widest point, slightly pressing your thumb to the palm
Measure with measuring tape loose. It should fit my wrist, but not tight, loose and soft.
You have two numbers between them and have to get the size of your bracelet.
In average to this size need add 3-6 inches to the length of its wrist for freedom of fit, given the design of the future bracelet.