Here’s a full ring size conversion for Hong Kong, United States, United Kingdom, Japan, Circumference and diameter. In Singapore, many different jewellers use different units of measurement for their ring sizes. Here at Luna, we stuck to HK ring size because it is the most popular ring size unit used in Singapore.

 

Inter- Diameter (mm)	Circumference (mm)	HK Size	US Size	UK Size	Japan Size
14.1	44.3	6	3	F	4
14.3	44.9	7	3.25	F 1/2	5
14.7	46.2	8	3.75	G	6
14.9	46.8	9	4	H	7
15.3	48.1	10	4.5	I	8
15.7	49.3	11	5	J 1/2	9
16.1	50.6	12	5.5	K 1/2	10
16.5	51.8	13	6	L 1/2	11
16.7	52.5	14	6.25	M	12
17.1	53.7	15	6.75	N	13.5
17.3	54.3	16	7	N 1/2	14
17.7	55.6	17	7.5	O 1/2	15
18.2	57.2	18	8	P 1/2	16.25
18.5	58.1	19	8.5	Q 1/2	17
18.8	59.1	20	9.75	R	17.5
19.1	60.0	21	9.25	S	18
19.4	60.9	22	9.5	S 1/2	19
19.8	62.2	23	10	T 1/2	20
20.2	63.5	24	10.5	U 1/2	22
20.6	64.7	25	11	V 1/2	23
21	66.0	26	11.5	W 1/2	24
21.2	66.6	27	12	X	24.5
21.6	67.9	28	12.25	Y	25.5
22	69.1	29	12.5	Z 1/2	26.5