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RingSizeConvert.com

Convert MM to Ring Size

Millimeters are the most precise unit for ring sizing — enter your measurement below and we'll match it to a standard size.

How would you like to find your size?

Measure the inside diameter of the ring — straight across the inner hole, not the outside of the band.

Lay the ring flat and measure straight across the inside edge.

Is your mm number a diameter or a circumference?

This is the single most common mix-up when converting a millimeter measurement.

  • Diameter is the straight-line width across the inside of an existing ring — typically 14-23mm for adult sizes. Use "I have a ring" above.
  • Circumference is the distance around a string or paper strip wrapped around your finger — typically 44-70mm for adult sizes. Use "I measured my finger" above.

Quick mm reference

Common sizes and their millimeter measurements, at a glance.

Common ring sizes in millimeters
US / CanadaUS, CA, MXUK / AustraliaUK, IE, AU, NZ, ZAEUEU, FR, AT, BE, DK, SE, NO, FIGermany / NetherlandsDE, NLJapanJP, CN, KR, HK, SGIndia (Bluestone)India (Jewelove)India (VowJewels)India (The Vedic Crystals)Diameter (mm)Circumference (mm)
US / CanadaUS, CA, MX4UK / AustraliaUK, IE, AU, NZ, ZAHEUEU, FR, AT, BE, DK, SE, NO, FI47Germany / NetherlandsDE, NL15JapanJP, CN, KR, HK, SG7India (Bluestone)6.75India (Jewelove)6.75India (VowJewels)6India (The Vedic Crystals)7Diameter (mm)14.88Circumference (mm)46.75
US / CanadaUS, CA, MX5UK / AustraliaUK, IE, AU, NZ, ZAJ½EUEU, FR, AT, BE, DK, SE, NO, FI49.5Germany / NetherlandsDE, NL15.5JapanJP, CN, KR, HK, SG9India (Bluestone)9.32India (Jewelove)9.32India (VowJewels)8India (The Vedic Crystals)9Diameter (mm)15.7Circumference (mm)49.32
US / CanadaUS, CA, MX6UK / AustraliaUK, IE, AU, NZ, ZAL½EUEU, FR, AT, BE, DK, SE, NO, FI52Germany / NetherlandsDE, NL16.5JapanJP, CN, KR, HK, SG11India (Bluestone)11.87India (Jewelove)11.87India (VowJewels)10India (The Vedic Crystals)11Diameter (mm)16.51Circumference (mm)51.87
US / CanadaUS, CA, MX7UK / AustraliaUK, IE, AU, NZ, ZAN½EUEU, FR, AT, BE, DK, SE, NO, FI54.5Germany / NetherlandsDE, NL17.5JapanJP, CN, KR, HK, SG14India (Bluestone)14.41India (Jewelove)14.41India (VowJewels)12India (The Vedic Crystals)13Diameter (mm)17.32Circumference (mm)54.41
US / CanadaUS, CA, MX8UK / AustraliaUK, IE, AU, NZ, ZAP½EUEU, FR, AT, BE, DK, SE, NO, FI57Germany / NetherlandsDE, NL18JapanJP, CN, KR, HK, SG16India (Bluestone)16.99India (Jewelove)16.99India (VowJewels)14India (The Vedic Crystals)15Diameter (mm)18.14Circumference (mm)56.99
US / CanadaUS, CA, MX9UK / AustraliaUK, IE, AU, NZ, ZAR½EUEU, FR, AT, BE, DK, SE, NO, FI59.5Germany / NetherlandsDE, NL19JapanJP, CN, KR, HK, SG18India (Bluestone)19.53India (Jewelove)19.53India (VowJewels)16India (The Vedic Crystals)17Diameter (mm)18.95Circumference (mm)59.53
US / CanadaUS, CA, MX10UK / AustraliaUK, IE, AU, NZ, ZAT½EUEU, FR, AT, BE, DK, SE, NO, FI62Germany / NetherlandsDE, NL20JapanJP, CN, KR, HK, SG20India (Bluestone)22.08India (Jewelove)22.08India (VowJewels)18India (The Vedic Crystals)19Diameter (mm)19.76Circumference (mm)62.08
US / CanadaUS, CA, MX11UK / AustraliaUK, IE, AU, NZ, ZAV½EUEU, FR, AT, BE, DK, SE, NO, FI64.5Germany / NetherlandsDE, NL20.5JapanJP, CN, KR, HK, SG23India (Bluestone)24.62India (Jewelove)24.62India (VowJewels)20India (The Vedic Crystals)21Diameter (mm)20.57Circumference (mm)64.62
US / CanadaUS, CA, MX12UK / AustraliaUK, IE, AU, NZ, ZAX½EUEU, FR, AT, BE, DK, SE, NO, FI67Germany / NetherlandsDE, NL21.5JapanJP, CN, KR, HK, SG25India (Bluestone)27.2India (Jewelove)27.2India (VowJewels)22India (The Vedic Crystals)23Diameter (mm)21.39Circumference (mm)67.2

View the full ring size chart →