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US ring size 10½

A US size 10½ ring is 20.16 mm (0.794") across the inside and 63.3 mm (2.49") round. It converts to UK U½, EU 63, Japan 22 and Swiss 23.5. The 1:1 circle below is already set to size 10½: 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 10½20.16 mm · 0.794" inside · 63.3 mm round
Inside diameter20.16 mm
Band wall1.8 mm
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Full chart 19 rows

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Size 10½ and the quarter sizes around it

9 rows
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US ring size 10.5 and quarter sizes within one size either side: inside diameter, difference in mm, circumference, UK and EU sizes
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19.35−0.81 mm60.8S½61
19.55−0.61 mm61.4T61
19.76−0.41 mm62.1T½62
19.96−0.20 mm62.7U63
20.16—63.3U½63
20.37+0.20 mm64.0V64
20.57+0.41 mm64.6V½65
20.77+0.61 mm65.3W65
20.98+0.81 mm65.9W½66

Ordering a size 10½ in different band widths

4 rows
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What size to order for a US size 10.5 finger in narrow, 4–6 mm, 7 mm and wider, and comfort-fit bands
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10½20.16Bands under 4 mm usually fit true to size.
10¾–1120.37–20.57A 4–6 mm band covers more skin and feels snugger: jewellers suggest a quarter to a half size up.
11–11½20.57–20.98Wide and cigar bands grip the whole finger segment: half a size to a full size up.
10–10¼19.76–19.96A domed comfort-fit inside slips over the knuckle more easily: often a quarter to a half size down.

Blank length for a size 10½ band

6 rows
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Length of wire or sheet to cut for a US size 10.5 ring band (20.16 mm inside) in stock 1.0 to 2.5 mm thick, by π × (inside diameter + thickness)
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66.52.618"22.16
67.12.642"22.56
68.12.680"23.16
69.02.717"23.76
69.62.741"24.16
71.22.803"25.16

05 / Field guide

Size 10½,
20.16 mm inside.

Everything about a US 10½: 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 10 and size 11.

Who wears a size 10½

A US 10½ 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 10½ is 3.5 sizes above the usual women’s size and 0.5 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 10 (19.76 mm) and 0.41 mm narrower than a 11 (20.57 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 10½ by most of a size.

Size 10½ in the UK, Europe and Japan

A 10½ is 63.3 mm round. UK letters on the BS 6820 scale cover 0.625 mm each with half sizes, and U½ runs from 62.81 to 63.44 mm, so a 10½ sits near the top of U½. If you are on the large side of a 10½, a UK V may suit better.

ISO 8653 rounds to the nearest millimetre, so EU 63 covers 62.5 to 63.5 mm and a 10½ lands 0.85 mm into that band. Swiss and Italian sizes subtract 40, giving 23.5. Japan 22 is 20.0 mm inside, 0.16 mm smaller than a US 10½, so Japanese 22 is the nearest match.

Quarter sizes either side

A 10¼ is 19.96 mm and a 10¾ is 20.37 mm, each about 0.2 mm from a 10½: roughly the thickness of two sheets of paper on the diameter. If your ring falls between 10¼ and 10¾ on the 1:1 circle, order a 10½ for a band under 4 mm.

For a 4–6 mm band, jewellers suggest 10¾ to 11; for 7 mm and wider, 11 to 11½; for a comfort-fit inside, 10 to 10¼. Smart-ring kits that include a size 11 sample: Oura Ring 4, Galaxy Ring, Ring AIR.

Making a size 10½ band

The blank length is the circumference of the middle of the band wall: π × (20.16 + thickness). Cut 68.1 mm of 1.5 mm stock or 69.6 mm of 2.0 mm stock, and the finished band has an outside diameter of 23.16 or 24.16 mm. Leave a little extra for filing the joint, and true the band on a mandrel at 10½ after soldering.

Blank = π × (20.16 mm + t) · 1.5 mm → 68.1 mm · 2.0 mm → 69.6 mm

Questions

Answered plainly.

01What is a size 10½ ring in mm?+

A US size 10½ ring is 20.16 mm (0.794") across the inside, with an inside circumference of 63.3 mm (2.49").

02What is a US size 10½ in UK and EU sizes?+

US 10½ is UK U½ and EU (ISO 8653) 63. It is also Japan 22 and Swiss 23.5.

03How much bigger is a size 11 than a size 10½?+

A size 11 is 0.41 mm wider inside (20.57 against 20.16 mm) and 1.28 mm longer round.

04How long a blank do I cut for a size 10½ ring?+

68.1 mm for 1.5 mm thick stock and 69.6 mm for 2.0 mm, from π × (20.16 mm + thickness).

05Should I order a size 10½ for a wide band?+

For a band 7 mm or wider, jewellers suggest 11 to 11½; for 4–6 mm, 10¾ to 11. Under 4 mm, a 10½ fits true to size.

Ring sizesUS · inside Ø mm

Carat sizes

Necklace lengths