The wrist is only part of the fitting. A closed bangle needs to pass over your hand, and a hinged bangle needs a clasp you can operate on the wrist where you plan to wear it.
Slide a closed bangle on and off
Draw your thumb towards your palm and ease the bangle over your knuckles. Try another size if it takes force. With the bangle on, lower your hand, then make sure you can remove it comfortably.
Practise fastening a hinged bangle
Ask the jeweller how the clasp and any safety catch work. Put it on your usual wrist and close it with the opposite hand. Check that both ends meet properly and that you can release it again.
Keep the measurements for that design
Note the inner diameter for a round bangle, or the two inside dimensions for an oval one. Keep the model code with those figures if you want to find the same fit later.
