Ring Size Converter

How to measure

Find your ring size at home

• Paper strip methodCut a strip of paper about 80 mm long and 6 mm wide. Wrap it snugly around the base of the finger, mark where it overlaps, and measure the marked length in millimeters with a ruler. The result is the inner circumference. Type it into the converter above using Inner circumference (mm).
• Existing ring methodPlace a ring that already fits on a ruler with millimeter markings. Read the straight-across distance from the inside of one side of the band to the inside of the other. This is the inner diameter; type it into the converter using Inner diameter (mm).
• Mandrel or sizer setA jeweler reads size from a numbered mandrel after sliding the ring on, or from a graduated plastic sizer set. The number on the mandrel is usually the US size for North American jewelers and the EU mm for European jewelers.
• Measure at the right timeFingers swell with heat, exercise, salty meals and water retention. Measure later in the day at a normal temperature for the best fit, and average two or three measurements.

How ring sizing works

What each size system measures

• US / Canada scaleWhole and half steps from about 1 to 15. One whole step is roughly 0.41 mm of inner diameter (about 1.27 mm of circumference), so a US 7 to US 8 jump is about 1.3 mm around the inside.
• UK letter scaleLetters A through Z plus halves (and Z+1, Z+2 for extended sizes), used by jewelers in the UK, Ireland, Australia and New Zealand. Two UK letters equal about one US size.
• EU / ISO 8653The European standard reports inner circumference as a whole number of millimeters (44, 45, 46, ...). EU 54 means an inner circumference of 54 mm, which works out to about US 7.
• JP / CN / KR scaleThe JIS S 6310 standard in Japan numbers sizes from about 1 to 27 in single steps. Mainland Chinese and Korean charts published by most online retailers align with the same integer scale.
• Comfort-fit and wide bandsA wide or comfort-fit band sits differently on the finger and often fits a half size smaller than a thin band. Many jewelers recommend going up one half size for a band 6 mm wide or wider.

Brand-to-brand variation is real and is usually within plus or minus a half size. Use the chart as a starting point and try the ring in person when possible. The conversion runs entirely in your browser and nothing is uploaded.