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US ring size 6½

A US size 6½ ring is 16.91 mm (0.666") across the inside and 53.1 mm (2.09") round. It converts to UK M½, EU 53, Japan 13 and Swiss 13. The 1:1 circle below is already set to size 6½: 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 6½16.91 mm · 0.666" inside · 53.1 mm round
Inside diameter16.91 mm
Band wall1.8 mm
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Full chart 19 rows

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Size 6½ and the quarter sizes around it

9 rows
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US ring size 6.5 and quarter sizes within one size either side: inside diameter, difference in mm, circumference, UK and EU sizes
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16.10−0.81 mm50.6K½51
16.30−0.61 mm51.2L51
16.51−0.41 mm51.9L½52
16.71−0.20 mm52.5M52
16.91—53.1M½53
17.12+0.20 mm53.8N54
17.32+0.41 mm54.4N½54
17.52+0.61 mm55.0O55
17.73+0.81 mm55.7O½56

Ordering a size 6½ in different band widths

4 rows
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What size to order for a US size 6.5 finger in narrow, 4–6 mm, 7 mm and wider, and comfort-fit bands
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6½16.91Bands under 4 mm usually fit true to size.
6¾–717.12–17.32A 4–6 mm band covers more skin and feels snugger: jewellers suggest a quarter to a half size up.
7–7½17.32–17.73Wide and cigar bands grip the whole finger segment: half a size to a full size up.
6–6¼16.51–16.71A domed comfort-fit inside slips over the knuckle more easily: often a quarter to a half size down.

Blank length for a size 6½ band

6 rows
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Length of wire or sheet to cut for a US size 6.5 ring band (16.91 mm inside) in stock 1.0 to 2.5 mm thick, by π × (inside diameter + thickness)
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56.32.216"18.91
56.92.240"19.31
57.82.277"19.91
58.82.315"20.51
59.42.339"20.91
61.02.401"21.91

05 / Field guide

Size 6½,
16.91 mm inside.

Everything about a US 6½: 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 6 and size 7.

Who wears a size 6½

A US 6½ is in the main women’s range (most women wear 6 to 8½), just under the most common women’s size, 7. Jewellers’ order data puts the most common women’s size at 7 and men’s at 10, so a 6½ is 0.5 sizes below the usual women’s size and 3.5 sizes below 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 6 (16.51 mm) and 0.41 mm narrower than a 7 (17.32 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 6½ by most of a size.

Size 6½ in the UK, Europe and Japan

A 6½ is 53.1 mm round. UK letters on the BS 6820 scale cover 0.625 mm each with half sizes, and M½ runs from 52.81 to 53.44 mm, so a 6½ sits in the middle of M½. It converts cleanly, so a UK M½ ring should feel the same.

ISO 8653 rounds to the nearest millimetre, so EU 53 covers 52.5 to 53.5 mm and a 6½ lands 0.63 mm into that band. Swiss and Italian sizes subtract 40, giving 13. Japan 13 is 17.0 mm inside, 0.09 mm larger than a US 6½, so Japanese 13 is the nearest match.

Quarter sizes either side

A 6¼ is 16.71 mm and a 6¾ is 17.12 mm, each about 0.2 mm from a 6½: roughly the thickness of two sheets of paper on the diameter. If your ring falls between 6¼ and 6¾ on the 1:1 circle, order a 6½ for a band under 4 mm.

For a 4–6 mm band, jewellers suggest 6¾ to 7; for 7 mm and wider, 7 to 7½; for a comfort-fit inside, 6 to 6¼. Smart-ring kits that include a size 7 sample: Oura Ring 4, Galaxy Ring, Ring AIR.

Making a size 6½ band

The blank length is the circumference of the middle of the band wall: π × (16.91 + thickness). Cut 57.8 mm of 1.5 mm stock or 59.4 mm of 2.0 mm stock, and the finished band has an outside diameter of 19.91 or 20.91 mm. Leave a little extra for filing the joint, and true the band on a mandrel at 6½ after soldering.

Blank = π × (16.91 mm + t) · 1.5 mm → 57.8 mm · 2.0 mm → 59.4 mm

Questions

Answered plainly.

01What is a size 6½ ring in mm?+

A US size 6½ ring is 16.91 mm (0.666") across the inside, with an inside circumference of 53.1 mm (2.09").

02What is a US size 6½ in UK and EU sizes?+

US 6½ is UK M½ and EU (ISO 8653) 53. It is also Japan 13 and Swiss 13.

03How much bigger is a size 7 than a size 6½?+

A size 7 is 0.41 mm wider inside (17.32 against 16.91 mm) and 1.28 mm longer round.

04How long a blank do I cut for a size 6½ ring?+

57.8 mm for 1.5 mm thick stock and 59.4 mm for 2.0 mm, from π × (16.91 mm + thickness).

05Should I order a size 6½ for a wide band?+

For a band 7 mm or wider, jewellers suggest 7 to 7½; for 4–6 mm, 6¾ to 7. Under 4 mm, a 6½ fits true to size.

Ring sizesUS · inside Ø mm

Carat sizes

Necklace lengths