One size, several naming systems

Understand what changes when a ring size crosses borders.

Regional labels can differ even when the physical ring is similar. Keep the original label, measurement method, and converted direction together for a more useful review.

Open the size converter Start a ring with my size system

Illustrative sizing workbench. Keep the original measurement and system visible when converting; a nominal size alone does not explain fit.

Fit, wear & care—considered together

A clearer decision, with the important context kept beside it

Ring-size labels are different names for nearby physical dimensions. This guide shows what each system means before you use the converter.

Use this page when

You want to understand a chart mismatch before selecting a size.
You need to explain a known size to a jeweler in another country.

Pause and choose another path when

You have no original system or physical measurement.
You need a full converter result without opening the working tool.

Where this choice often matters

Buying from an international collection.
Translating a family ring’s record for a new custom piece.

Compare the details

System labels and their useful anchor

Keep the original label and its official measurement context visible, then compare it with the physical dimensions in Leyloon’s conversion table.

System	Label style	Useful anchor	Caution
US / Canada	Numbers and fractions	Named conversion table row	Not a millimeter value
UK / Australia	Letters and fractions	Named conversion table row	Charts may round differently
EU	Numeric convention	Inside-circumference context	State the table used
Japan	Numeric scale	Named conversion table	Preserve original label

Ring-size reference chart

Compare named sizes with inside measurements

Keep your original system and maker’s chart. This table is a comparison aid, not a universal fit promise.

Diameter inner edge to inner edge through the centerCircumference the complete inside path around the ringFit review intended finger, hand, band width, stack, and knuckle

US & Canada	UK, Europe & Australia	Asia	Inside diameter	Inside circumference
3	F	4	14.1 mm	44.3 mm
3.5	G	—	14.5 mm	45.6 mm
4	H	7	14.9 mm	46.8 mm
4.5	I	8	15.3 mm	48.1 mm
5	J	9	15.7 mm	49.3 mm
5.5	K	10	16.1 mm	50.6 mm
6	L	11	16.5 mm	51.8 mm
6.5	M	13	16.9 mm	53.1 mm
7	N	14	17.3 mm	54.3 mm
7.5	O	15	17.7 mm	55.6 mm
8	P	16	18.1 mm	56.9 mm
8.5	Q	17	18.5 mm	58.1 mm
9	R	18	19.0 mm	59.7 mm
9.5	S	19	19.4 mm	60.9 mm
10	T	20	19.8 mm	62.2 mm
10.5	U	22	20.2 mm	63.5 mm
11	V	23	20.6 mm	64.7 mm
11.5	W	24	21.0 mm	66.0 mm
12	X	25	21.4 mm	67.2 mm
12.5	Y	26	21.8 mm	68.5 mm
13	Z.5	27	22.2 mm	69.7 mm
13.5	Z1	—	22.6 mm	71.0 mm

Reviewed 2026-08-25. Source reference: GIA ring-size guide. This table follows GIA’s US and Canada, UK/Europe/Australia, and Asia columns; blank cells are not listed by GIA. Leyloon uses the nearest physical row without interpolation and keeps your original measurement beside it.

Keep your direction organised

The complete choice groups for this decision

Ring-size labels are different names for nearby physical dimensions. This guide shows what each system means before you use the converter. The groups below keep related choices together, and every selection stays editable when you continue.

What are you trying to understand?

Choose one direction.

A country labelSee how it maps physically.
A diameter or circumferenceKeep measurement type visible.
Two charts disagreeCompare sources and nearby rows.
A maker-specific chartPreserve that chart with the note.

What can confirm the conversion?

Keep every direction that fits.

Measure the existing ringAdds inside diameter.
Check the intended fingerAdds personal fit.
Confirm band widthAdds design context.
Professional gaugeTests the physical fit.

Questions worth asking

Open the concern that sounds like yours

Choose the question that sounds like yours. Each answer keeps the next step clear without closing decisions that still need review.

Which system is most accurate?

The physical measurement and correct fit matter more than the label; each system names table positions differently.

Why not use a formula for every system?

Named scales use conversion table mappings; they are not all simple formulas.

What if my size falls between chart rows?

Show both nearby rows and take the band and wearer context into review.

Ready when you are

Carry this direction into your design

Leyloon can keep these choices together while you continue. Every detail stays editable. Your choices stay editable as you continue.

Original label and physical comparisonNeeded before the direction is complete
Optional chart or receipt referenceKeep it open if you are still deciding
Intended widthA useful next question
Table mismatch or nearby rowsKeep it open if you are still deciding

Illustrative ring-wear context across three anatomically complete hands — Illustrative ring-wear context—not a size, width, or knuckle-fit comparison. Use the governed measurements and the exact planned ring construction together. Here it supports the decisions behind “Understand what changes when a ring size crosses borders.”

A visual map of this brief

See what stays known—and what remains open

This guide begins with “Separate the name of the size from the physical ring it describes.” The next choices stay grouped, editable, and connected to that same Atelier brief.

Ring you are sizingChoose the ring context so the measurement stays attached to the right width, profile, and finger.
What measurement do you have?Keep the method with the number. The working tool above can help compare it without replacing the maker's final fit check.
Band width or stackChoose the planned contact width. Exact millimeters stay editable.
What could change the fit?Choose the closest context. You can add the exact measurements privately in Atelier.

Start with what matters on this page

Keep the measurement with the ring it belongs to

Choose how you measured and the ring context. The number stays private, and Atelier carries the method, width, and fit notes together.

01 Ring you are sizing

Choose the ring context so the measurement stays attached to the right width, profile, and finger.

02 What measurement do you have?

Keep the method with the number. The working tool above can help compare it without replacing the maker's final fit check.

03 Band width or stack

Choose the planned contact width. Exact millimeters stay editable.

04 What could change the fit?

Choose the closest context. You can add the exact measurements privately in Atelier.

What else should Atelier help with?

Add only the parts you want to explore. The page topic is already included.

Fit and formIncluded from this page

Nothing selected yet. You can still continue and answer in Atelier.

Published customer proof

Real experiences, kept separate from promises

Only approved purchase-linked reviews appear here. An illustrative scene is never presented as a customer, and one person’s experience is never treated as a promise for another piece.

See what Leyloon customers have shared

Read recent shop reviews on Etsy, then come back when you are ready to shape your own fit and jewelry direction.

See Leyloon reviews on Etsy

These reviews reflect individual Leyloon service experiences. Your fit and jewelry direction and quote request are reviewed on their own.