Ring Size Converter

Enter the ring size you already know and instantly see the diameter (mm), European circumference (mm), US and UK equivalents. Unlike shoe sizes, ring sizing does not vary by brand — the jewelry industry uses one standard chart worldwide.

Known SystemValue

Matching Sizes

Diameter (mm)16.9 mm

Europe (mm)53.1 mm

US6.5

UKM

Ring size chart
Diameter (mm)	Europe (mm)	US	UK
14 mm	44 mm	3	F
14.4 mm	45.5 mm	3.5	G
14.9 mm	46.8 mm	4	H
15.3 mm	48 mm	4.5	I
15.7 mm	49.3 mm	5	J
16.1 mm	50.6 mm	5.5	K
16.5 mm	51.8 mm	6	L
16.9 mm	53.1 mm	6.5	M
17.3 mm	54.4 mm	7	N
17.7 mm	55.7 mm	7.5	O
18.2 mm	57 mm	8	P
18.6 mm	58.3 mm	8.5	Q
19 mm	59.5 mm	9	R
19.4 mm	60.8 mm	9.5	S
19.8 mm	62.1 mm	10	T
20.2 mm	63.4 mm	10.5	U
20.6 mm	64.6 mm	11	V
21 mm	65.9 mm	11.5	W
21.4 mm	67.2 mm	12	X

How is ring size determined?

Ring size is most reliably expressed as the inside diameter of the ring in millimeters. The European system uses inside circumference directly — diameter and circumference are related by simple geometry (circumference = diameter × π), so the conversion between them is always exact. US and UK systems use their own numbered and lettered scales; this chart is compiled from the standard international jewelry sizing reference.

For the most accurate result, measure the inside diameter of a ring that already fits with a ruler and select the closest value under "Diameter (mm)".

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