As part of an adjustable ring, you can take the finger tour easily with a piece of tape. Tighten hard, and postpone the measurement to a rule. Below an example in size 54. A size = 1 millimeter. 

 

If you have a ring at the right one size, Download the Baguier to print here To know the size one of your ring

 

 

As part of a gift without any specific data possible. Refer to this table. Ask to reach an additional entrance to your gift, we offer it with pleasure. 

Size Ue millimeter	Diameter in mm	Estimate annular
40/46	12,7 / 14,6	XXS
47/48	15 / 15,3	XS
49/53	15,6 / 16,9	S
54/57	17,2 / 18,2	M
58/63	18,5 /  20	L
64/70	20,3 / 22	XL
71/76	22,3 / 23,9	Xxl
76 and +	Size split by 3.14 = Diameter	Xxxl