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US ring size 12

A US size 12 ring is 21.38 mm (0.842") across the inside and 67.2 mm (2.64") round. It converts to UK X½, EU 67, Japan 26 and Swiss 27. The 1:1 circle below is already set to size 12: lay a ring on it to check yours.

Try

Lay a ring that fits flat on the circle and size the red line until it just touches the inside edge of the band all the way round: on a phone, slide sideways anywhere on the stage or hold the buttons below; on a computer, drag the edge, scroll or press ← →. The gold ring is the band’s wall: don’t match its outside.

US 1221.38 mm · 0.842" inside · 67.2 mm round
Inside diameter21.38 mm
Band wall1.8 mm
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Full chart 19 rows

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Size 12 and the quarter sizes around it

9 rows
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US ring size 12 and quarter sizes within one size either side: inside diameter, difference in mm, circumference, UK and EU sizes
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20.57−0.81 mm64.6V½65
20.77−0.61 mm65.3W65
20.98−0.41 mm65.9W½66
21.18−0.20 mm66.5X67
21.38—67.2X½67
21.59+0.20 mm67.8Y½68
21.79+0.41 mm68.5Z68
21.99+0.61 mm69.1Z½69
22.20+0.81 mm69.7Z+170

Ordering a size 12 in different band widths

4 rows
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What size to order for a US size 12 finger in narrow, 4–6 mm, 7 mm and wider, and comfort-fit bands
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1221.38Bands under 4 mm usually fit true to size.
12¼–12½21.59–21.79A 4–6 mm band covers more skin and feels snugger: jewellers suggest a quarter to a half size up.
12½–1321.79–22.20Wide and cigar bands grip the whole finger segment: half a size to a full size up.
11½–11¾20.98–21.18A domed comfort-fit inside slips over the knuckle more easily: often a quarter to a half size down.

Blank length for a size 12 band

6 rows
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Length of wire or sheet to cut for a US size 12 ring band (21.38 mm inside) in stock 1.0 to 2.5 mm thick, by π × (inside diameter + thickness)
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70.32.769"23.38
70.92.793"23.78
71.92.830"24.38
72.82.867"24.98
73.52.892"25.38
75.02.954"26.38

05 / Field guide

Size 12,
21.38 mm inside.

Everything about a US 12: what it measures, who usually wears it, how it converts in each country, the quarter sizes around it and what to order for wide bands. Neighbouring sheets: size 11½ and size 12½.

Who wears a size 12

A US 12 is squarely in the men’s range (most men wear 9 to 12), and a common thumb-ring size for women. Jewellers’ order data puts the most common women’s size at 7 and men’s at 10, so a 12 is 5 sizes above the usual women’s size and 2 sizes above the usual men’s size. The same finger is often a quarter to half size larger on the dominant hand.

It is 0.41 mm wider inside than a 11½ (20.98 mm) and 0.41 mm narrower than a 12½ (21.79 mm). On the circumference that is 1.28 mm per half size, which is why a strip of string, stretching a couple of millimetres as you pull it snug, can misread a 12 by most of a size.

Size 12 in the UK, Europe and Japan

A 12 is 67.2 mm round. UK letters on the BS 6820 scale cover 0.625 mm each with half sizes, and X½ runs from 66.56 to 67.19 mm, so a 12 sits near the top of X½. If you are on the large side of a 12, a UK Y may suit better.

ISO 8653 rounds to the nearest millimetre, so EU 67 covers 66.5 to 67.5 mm and a 12 lands 0.68 mm into that band. Swiss and Italian sizes subtract 40, giving 27. Japan 26 is 21.3 mm inside, 0.08 mm smaller than a US 12, so Japanese 26 is the nearest match.

Quarter sizes either side

A 11¾ is 21.18 mm and a 12¼ is 21.59 mm, each about 0.2 mm from a 12: roughly the thickness of two sheets of paper on the diameter. If your ring falls between 11¾ and 12¼ on the 1:1 circle, order a 12 for a band under 4 mm.

For a 4–6 mm band, jewellers suggest 12¼ to 12½; for 7 mm and wider, 12½ to 13; for a comfort-fit inside, 11½ to 11¾. Smart-ring kits that include a size 12 sample: Oura Ring 4, Galaxy Ring, Ring AIR.

Making a size 12 band

The blank length is the circumference of the middle of the band wall: π × (21.38 + thickness). Cut 71.9 mm of 1.5 mm stock or 73.5 mm of 2.0 mm stock, and the finished band has an outside diameter of 24.38 or 25.38 mm. Leave a little extra for filing the joint, and true the band on a mandrel at 12 after soldering.

Blank = π × (21.38 mm + t) · 1.5 mm → 71.9 mm · 2.0 mm → 73.5 mm

Questions

Answered plainly.

01What is a size 12 ring in mm?+

A US size 12 ring is 21.38 mm (0.842") across the inside, with an inside circumference of 67.2 mm (2.64").

02What is a US size 12 in UK and EU sizes?+

US 12 is UK X½ and EU (ISO 8653) 67. It is also Japan 26 and Swiss 27.

03How much bigger is a size 12½ than a size 12?+

A size 12½ is 0.41 mm wider inside (21.79 against 21.38 mm) and 1.28 mm longer round.

04How long a blank do I cut for a size 12 ring?+

71.9 mm for 1.5 mm thick stock and 73.5 mm for 2.0 mm, from π × (21.38 mm + thickness).

05Should I order a size 12 for a wide band?+

For a band 7 mm or wider, jewellers suggest 12½ to 13; for 4–6 mm, 12¼ to 12½. Under 4 mm, a 12 fits true to size.

Ring sizesUS · inside Ø mm

Carat sizes

Necklace lengths