Ring Size mm to Inches Converter

Enter ring diameter or circumference, convert between units and US, UK/AU, EU, India standards

Ring Size mm to Inches Chart

Read diameter and circumference in mm and inches first, then scan the full set of international ring size standards in the same table.

Measurement type

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Unit

Diameter (mm)	Diameter (inches)	Circumference (mm)	Circumference (inches)	US & Canada	UK & Australia	EU	South Asia (IN)	Central Europe (Latin)	Japan, Singapore & Taiwan	Hong Kong	Brazil	Russia	Turkey (Local)
14.05	0.55	44.14	1.74	3	F	44	4	4	4	7	4	14.05	4
14.25	0.56	44.77	1.76	3.25	G	45	5	5	5	7.5	5	14.25	5
14.45	0.57	45.40	1.79	3.5	G 1/2	45.5	5.5	5.5	5.5	8	6	14.45	6
14.65	0.58	46.02	1.81	3.75	H	46	6	6	6	8.5-9	7	14.65	7
14.86	0.59	46.68	1.84	4	H 1/2	47	7	7	7	9.5	8	14.86	8
15.04	0.59	47.25	1.86	4.25	I	47.5	7.5	7.5	7.5	10	9	15.04	8.5
15.27	0.60	47.97	1.89	4.5	J	48	8	8	8	10.5	10	15.27	9
15.40	0.61	48.38	1.90	4.75	J 1/2	48.5	8.5	8.5	8.5	11	11	15.4	10
15.70	0.62	49.32	1.94	5	K 1/2	49.5	9	9.5	9	11.5-12	12	15.7	11
15.90	0.63	49.95	1.97	5.25	L	50	10	10	9.5	12.5	13	15.9	12
16.10	0.63	50.58	1.99	5.5	L 1/2	50.5	11	10.5	10.5	13	14	16.1	12.5
16.30	0.64	51.21	2.02	5.75	M	51	11.5	11	11	13.5	15	16.3	13
16.51	0.65	51.87	2.04	6	M 1/2	52	12	12	12	14-14.5	16	16.51	14
16.71	0.66	52.50	2.07	6.25	N	52.5	13	12.5	12.5	15	17	16.71	15
16.92	0.67	53.16	2.09	6.5	N 1/2	53	14	13	13	15.5	18	16.92	16
17.12	0.67	53.78	2.12	6.75	O	54	15	14	13.5	16	19	17.12	16.5
17.32	0.68	54.41	2.14	7	O 1/2	54.5	16	14.5	14	16.5	20	17.32	17
17.53	0.69	55.07	2.17	7.25	P	55	17	15	14.5	17	21	17.53	18
17.73	0.70	55.70	2.19	7.5	P 1/2	56	17.5	16	15	17.5	22	17.73	19
17.93	0.71	56.33	2.22	7.75	Q	56.5	18	16.5	16	18	23	17.93	20
18.14	0.71	56.99	2.24	8	Q 1/2	57	19	17	16.5	18.5	24	18.14	21
18.34	0.72	57.62	2.27	8.25	R	57.5	20	17.5	17	19	25	18.34	22
18.54	0.73	58.25	2.29	8.5	R 1/2	58.5	21	18.5	17.5	19.5-20	26	18.54	23
18.75	0.74	58.91	2.32	8.75	S	59	21.5	19	18	20.5	27	18.75	24
18.95	0.75	59.53	2.34	9	S 1/2	59.5	22	19.5	18.5	21	28	18.95	25
19.15	0.75	60.16	2.37	9.25	T	60	23	20	19	21.5	29	19.15	25.5
19.35	0.76	60.79	2.39	9.5	T 1/2	61	24	21	19.5	22	30	19.35	26
19.56	0.77	61.45	2.42	9.75	U	61.5	25	21.5	20	22.5-23	31	19.56	27
19.76	0.78	62.08	2.44	10	U 1/2	62	26	22	21	23.5	32	19.76	28
19.96	0.79	62.71	2.47	10.25	V	63	26.5	23	22	24	33	19.96	29
20.17	0.79	63.37	2.49	10.5	V 1/2	63.5	27	23.5	22.5	24.5	33	20.17	30
20.37	0.80	64	2.52	10.75	W	64	28	24	23	25	—	20.37	31
20.57	0.81	64.62	2.54	11	W 1/2	64.5	29	24.5	24	25.5-26	—	20.57	32
20.78	0.82	65.28	2.57	11.25	X	65.5	29.5	25.5	25	26.5	—	20.78	33
20.98	0.83	65.91	2.59	11.5	X 1/2	66	30	26	25.5	27	—	20.98	34
21.18	0.83	66.54	2.62	11.75	Y	66.5	31	26.5	26	27.5	—	21.18	35
21.39	0.84	67.20	2.65	12	Y 1/2	67	32	27	27	28-28.5	—	21.39	36
21.59	0.85	67.83	2.67	12.25	Z	68	32.5	28	27.5	29	—	21.59	37
21.79	0.86	68.46	2.70	12.5	Z 1/2	68.5	33	28.5	28	29.5-30	—	21.79	38
21.99	0.87	69.09	2.72	12.75	Z+1	69	34	29	29	30.5	—	21.99	39
22.20	0.87	69.74	2.75	13	Z+1 1/2	70	35	30	30	31-31.5	—	22.2	40
22.40	0.88	70.37	2.77	13.25	Z+2	70.5	35.5	30.5	31	32	—	22.4	41
22.61	0.89	71.03	2.80	13.5	Z+2 1/2	71	36	31	32	32.5-33	—	22.61	42

About these standards

Values are based on commonly referenced international charts. Manufacturers may vary; use as guidance.

US/CA (United States and Canada):: Numeric scale with half and quarter sizes (e.g., 6, 6.25).
UK/AU (United Kingdom and Australia):: Alphabetic scale with half-steps (e.g., M, M½).
EU/FR/DE/ES (Europe, France, Germany, and Spain):: Metric system based on inner circumference in mm (e.g., 52, 54).
IN/PK/BD (India, Pakistan, and Bangladesh):: Numeric scale widely used in South Asia.
Central Europe (Latin):: Used in Italy (IT), Switzerland (CH), Spain (ES), Poland (PL), Netherlands (NL), Austria (AT), Czech Republic (CZ) and Slovakia (SK); size = inner circumference (mm) − 40 (e.g., 54 mm → Size 14).
JP/SG/TW (Japan, Singapore, and Taiwan):: "International Size" numeric scale widely seen in Asian markets (e.g., 12, 14).
HK (Hong Kong):: Local jeweler numeric scale; may include fractional/range steps (e.g., 15, 16).
RU (Russia):: Size is based on inner diameter in mm. In retail it's often shown in 0.5 steps (e.g., 17, 17.5, 18), but our chart lists more precise reference values (may include decimals) for comparison.
BR (Brazil):: Local numeric scale with its own rounding/labeling conventions, distinct from EU sizes (e.g., 14, 15).
TR (Turkey local):: Local offset/rounding conventions; may differ by chart (e.g., 14, 15). Often referred to as the Numara system in Turkey.

Ring Size Standards Overview

Guides & Tips

Practical tips for measuring ring diameter or circumference, converting mm and inches, and comparing common international standards.

1. Master the most accurate methods to measure your ring size at home for a perfect fit.
- Use a flexible measuring tape or piece of string to wrap around your finger, marking where the ends overlap for precise measurement.
- Measure both your knuckle and the base of your finger, then choose a size between these two measurements for optimal comfort.
- For best results, measure your finger at the end of the day when it's slightly larger, and avoid measuring when your hands are cold.
- Use a printable ring size chart or adjustable ring sizer tool for the most accurate at-home sizing experience.
- Use our online calculator to instantly determine your precise size, or get professionally measured for important purchases.
2. Convert mm to inches instantly: simple formula for ring diameter conversion
- To convert millimeters to inches, divide the mm value by 25.4 (for example, 16.5mm ÷ 25.4 = 0.65 inches), which is the standard conversion formula used throughout the jewelry industry.
- For quick reference, common ring diameters include 16mm (0.63 inches), 17mm (0.67 inches), and 18mm (0.71 inches), corresponding to US sizes 6, 7, and 8 respectively.
- When converting inches to mm, multiply by 25.4 instead (for example, 0.65 inches × 25.4 = 16.5mm), making it easy to convert in both directions for international ring sizing.
- Memorize the conversion that 1 inch equals exactly 25.4mm - this precise number ensures accurate ring sizing without rounding errors that could affect fit.
- Use our ring size converter tool to instantly see mm to inches conversions alongside matching ring sizes across US, UK, European, and Asian sizing systems.
3. Common ring sizes in mm, inches, and international size equivalents (US/UK/EU/India)
- US Size 4.5 equals 15.27mm diameter (0.60 inches), UK Size J, Europe Size 48, India Size 8 - one of the smaller common sizes available internationally.
- US Size 6 equals 16.51mm diameter (0.65 inches), UK Size M 1/2, Europe Size 52, India Size 12 - this is one of the most frequently purchased ring sizes in the United States.
- US Size 7 equals 17.32mm diameter (0.68 inches), UK Size O 1/2, Europe Size 54.5, India Size 16 - serving as a very popular medium size across many international markets.
- US Size 8 equals 18.14mm diameter (0.71 inches), UK Size Q 1/2, Europe Size 57, India Size 19 - commonly found in both women's and men's ring collections.
4. Why mm is preferred over inches for ring sizing worldwide
- Millimeters offer much greater precision than inches because they're smaller units - 1mm equals only 0.039 inches, allowing for exact ring sizing without confusing fractions or decimals.
- The global jewelry industry universally uses millimeters because they're part of the metric system, making international ring size charts consistent and easier to understand across countries.
- Inches require fractions like 2 1/2 inches or decimals like 0.65 inches, which can be confusing, while mm provides clean whole numbers (16mm, 17mm, 18mm) that are simpler to communicate.
- All international ring size standards are based on millimeters - European sizing uses circumference in mm (typically 50-60mm), while US/UK sizing systems are derived from mm diameter measurements.
- When shopping internationally from mm-based countries, always verify your size by converting inches to mm first (multiply by 25.4) since most online jewelers display ring sizes using millimeters.

Your Ring Sizing Toolkit

Open the next tool when you need a ring size calculator, visualizer, or another conversion workflow.

About Sizepedia

A data-driven size knowledge base providing standards, datasets and practical tools.

Sizepedia.com is a size-focused encyclopedia and toolkit: we collect and curate public standards, manufacturer size charts, and industry references to build consistent conversion tables and reference data that clarify how different systems correspond. We currently prioritize and publish features for ring sizing, including online measurement tools, international conversion tables, and brand mappings. Over time we will expand to footwear, apparel, and additional sizing categories to deliver more data and practical tools. Our resources are provided as a best-effort guide to help you choose sizes with confidence; when an exact fit matters, combine our guidance with local measurement or manufacturer recommendations for final confirmation.

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