Country chart — International

International ring size conversion

Every system on this site, compared honestly: what each system actually measures, where the ladders line up, where they don't, and which systems are deliberately left out rather than guessed.

What each system actually measures

US / Canada — a lookup ladder

Numbers 3–13.5, half steps, about 0.41 mm diameter per half size. No formula — a published table. See the US page.

UK / Ireland / Australia / NZ — letters

Letters A–Z with half letters, about 1.27 mm circumference per whole letter. The same letters, but published millimetre values differ between UK and Australian retailers — see Australia below. See the UK page.

EU / ISO — circumference itself

ISO 8653:2016: size = inner circumference in mm. France uses the same number; Germany uses diameter in mm instead. See the EU page.

India — circumference minus 40

Numbers, 1 mm circumference per size, rule size ≈ circumference − 40, with ±1 disagreement across published tables. See the India page.

Australia — same letters, different millimetres

Australia uses the UK letter system, and many charts say the conversion is identical. The published Australian ladder below shows why this site still labels Australia approximate: an Australian L is 16.1 mm / 50.6 mm here, while the UK native L is 16.4 mm / 51.5 mm and the unified chart's L row is 16.51 mm / 51.9 mm. That is a half-letter-scale spread for the same letter, and the Australian source itself warns that Australian suppliers differ by up to about 0.3 mm for the same letter.

Australian native ring size ladder, letters J to U, with inner diameter and circumference.
Australia letter	Inner diameter	Inner circumference
J	15.4 mm	48.4 mm
K	15.8 mm	49.6 mm
L	16.1 mm	50.6 mm
M	16.5 mm	51.9 mm
N	16.9 mm	53.2 mm
O	17.4 mm	54.5 mm
P	17.8 mm	55.8 mm
Q	18.2 mm	57.2 mm
R	18.6 mm	58.5 mm
S	19.1 mm	60.0 mm
T	19.5 mm	61.3 mm
U	20.0 mm	62.9 mm

Source: Joseph George (Australia) — see references below. The unified chart's Australia column mirrors the UK column for consistency; this native ladder is the reason that column is labelled approximate.

Systems deliberately not shipped as definitive columns

Japan — cited, not adopted

Japanese sizes are often described as circumference − 40, the same rule as India — but published Japanese tables disagree by 1–2 sizes at larger sizes (for example, a 69.7 mm ring is Japanese 27 in one table and about 29 by the −40 rule). Until a primary Japanese source is verified, Japan is not a column here. Use millimetres with a Japanese seller.

Switzerland — circumference − 40, with fractions

Swiss sizes are also described as circumference − 40, but published Swiss tables use quarter fractions that do not line up consistently with the −40 rule. Not shipped as a definitive column for the same reason as Japan.

Brazil, China, Russia — not verified

These systems appear in some international tables, but no primary or consistently corroborated ladder was found in this research round. They are omitted rather than copied from a single secondary table. If a seller quotes one of these, ask for the millimetre diameter or circumference — that number converts anywhere.

Common sizes at a glance

Common ring sizes across systems.
US	UK (approx.)	EU	India (approx.)	Diameter	Circumference
6	L	52	12	16.51 mm	51.9 mm
7	N	54	14	17.32 mm	54.4 mm
8	P	57	17	18.14 mm	57.0 mm
9	R	60	20	18.95 mm	59.5 mm
10	T	62	22	19.76 mm	62.1 mm

Note: The safest international order is not a converted label at all: give the seller the inner diameter and circumference in millimetres. Every system on this page is, underneath, a label for those two numbers — and millimetres do not have a half-letter disagreement.

Original references

Related guides

International ring size chart
The full searchable table.
Ring size converter
Convert any system to any other system.
Measurement methodology
How the dataset is built and verified.