UK to US Ring Size

Enter a UK/Australia letter size below to find its US/Canada numeric equivalent, or browse the complete reference table.

Need to convert in reverse? Go to US to UK Ring Size Converter →

Common UK to US equivalents

These examples share the same inner diameter. Use the calculator for another size or an in-between measurement.

UK J½ corresponds to US 5 at 15.7 mm.
UK N½ corresponds to US 7 at 17.32 mm.
UK R½ corresponds to US 9 at 18.95 mm.

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Your size

Numeric size (e.g. 8) for US/Canada, EU, or Japan — or a letter size (e.g. P 1/2) for UK/Australia.

How to convert UK letter ring sizes to US numbers

British and Australian jewelers use an alphabetical letter scale (A through Z+4) where each step represents an increase in inside circumference. The US and Canadian standard uses numbers (3 to 13.5) anchored to inside diameter. Because letters and numbers describe different dimensions, the accurate method is converting through millimeter dimensions. For instance, UK size M corresponds to US 6¼ (16.7 mm diameter), while UK size N corresponds to US 6¾ (17.1 mm diameter).

UK to US reference table

UK to US ring size conversion
UK / AustraliaUK, IE, AU, NZ, ZA	US / CanadaUS, CA, MX	Diameter (mm)
UK / AustraliaUK, IE, AU, NZ, ZAF	US / CanadaUS, CA, MX3	Diameter (mm)14.07
UK / AustraliaUK, IE, AU, NZ, ZAG	US / CanadaUS, CA, MX3.5	Diameter (mm)14.48
UK / AustraliaUK, IE, AU, NZ, ZAH	US / CanadaUS, CA, MX4	Diameter (mm)14.88
UK / AustraliaUK, IE, AU, NZ, ZAI	US / CanadaUS, CA, MX4.5	Diameter (mm)15.29
UK / AustraliaUK, IE, AU, NZ, ZAJ½	US / CanadaUS, CA, MX5	Diameter (mm)15.7
UK / AustraliaUK, IE, AU, NZ, ZAK½	US / CanadaUS, CA, MX5.5	Diameter (mm)16.1
UK / AustraliaUK, IE, AU, NZ, ZAL½	US / CanadaUS, CA, MX6	Diameter (mm)16.51
UK / AustraliaUK, IE, AU, NZ, ZAM½	US / CanadaUS, CA, MX6.5	Diameter (mm)16.92
UK / AustraliaUK, IE, AU, NZ, ZAN½	US / CanadaUS, CA, MX7	Diameter (mm)17.32
UK / AustraliaUK, IE, AU, NZ, ZAO½	US / CanadaUS, CA, MX7.5	Diameter (mm)17.73
UK / AustraliaUK, IE, AU, NZ, ZAP½	US / CanadaUS, CA, MX8	Diameter (mm)18.14
UK / AustraliaUK, IE, AU, NZ, ZAQ¼	US / CanadaUS, CA, MX8.5	Diameter (mm)18.54
UK / AustraliaUK, IE, AU, NZ, ZAR½	US / CanadaUS, CA, MX9	Diameter (mm)18.95
UK / AustraliaUK, IE, AU, NZ, ZAS½	US / CanadaUS, CA, MX9.5	Diameter (mm)19.35
UK / AustraliaUK, IE, AU, NZ, ZAT½	US / CanadaUS, CA, MX10	Diameter (mm)19.76
UK / AustraliaUK, IE, AU, NZ, ZAU½	US / CanadaUS, CA, MX10.5	Diameter (mm)20.17
UK / AustraliaUK, IE, AU, NZ, ZAV½	US / CanadaUS, CA, MX11	Diameter (mm)20.57
UK / AustraliaUK, IE, AU, NZ, ZAW½	US / CanadaUS, CA, MX11.5	Diameter (mm)20.98
UK / AustraliaUK, IE, AU, NZ, ZAX½	US / CanadaUS, CA, MX12	Diameter (mm)21.39
UK / AustraliaUK, IE, AU, NZ, ZAY½	US / CanadaUS, CA, MX12.5	Diameter (mm)21.79
UK / AustraliaUK, IE, AU, NZ, ZAZ½	US / CanadaUS, CA, MX13	Diameter (mm)22.2