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US ring size 4½

A US size 4½ ring is 15.29 mm (0.602") across the inside and 48.0 mm (1.89") round. It converts to UK I½, EU 48, Japan 8 and Swiss 8. The 1:1 circle below is already set to size 4½: 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 4½15.29 mm · 0.602" inside · 48.0 mm round
Inside diameter15.29 mm
Band wall1.8 mm
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Full chart 19 rows

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Size 4½ and the quarter sizes around it

9 rows
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US ring size 4.5 and quarter sizes within one size either side: inside diameter, difference in mm, circumference, UK and EU sizes
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14.47−0.81 mm45.5G½45
14.68−0.61 mm46.1H46
14.88−0.41 mm46.8H½47
15.08−0.20 mm47.4I47
15.29—48.0I½48
15.49+0.20 mm48.7J49
15.69+0.41 mm49.3J½49
15.90+0.61 mm49.9K50
16.10+0.81 mm50.6K½51

Ordering a size 4½ in different band widths

4 rows
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What size to order for a US size 4.5 finger in narrow, 4–6 mm, 7 mm and wider, and comfort-fit bands
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4½15.29Bands under 4 mm usually fit true to size.
4¾–515.49–15.69A 4–6 mm band covers more skin and feels snugger: jewellers suggest a quarter to a half size up.
5–5½15.69–16.10Wide and cigar bands grip the whole finger segment: half a size to a full size up.
4–4¼14.88–15.08A domed comfort-fit inside slips over the knuckle more easily: often a quarter to a half size down.

Blank length for a size 4½ band

6 rows
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Length of wire or sheet to cut for a US size 4.5 ring band (15.29 mm inside) in stock 1.0 to 2.5 mm thick, by π × (inside diameter + thickness)
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51.22.015"17.29
51.82.039"17.69
52.72.076"18.29
53.72.113"18.89
54.32.138"19.29
55.92.200"20.29

05 / Field guide

Size 4½,
15.29 mm inside.

Everything about a US 4½: 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 4 and size 5.

Who wears a size 4½

A US 4½ is a smaller women’s size, below the 6 to 8½ range most women wear, and a common pinky size for men. Jewellers’ order data puts the most common women’s size at 7 and men’s at 10, so a 4½ is 2.5 sizes below the usual women’s size and 5.5 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 4 (14.88 mm) and 0.41 mm narrower than a 5 (15.69 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 4½ by most of a size.

Size 4½ in the UK, Europe and Japan

A 4½ is 48.0 mm round. UK letters on the BS 6820 scale cover 0.625 mm each with half sizes, and I½ runs from 47.81 to 48.44 mm, so a 4½ sits in the middle of I½. It converts cleanly, so a UK I½ ring should feel the same.

ISO 8653 rounds to the nearest millimetre, so EU 48 covers 47.5 to 48.5 mm and a 4½ lands 0.53 mm into that band. Swiss and Italian sizes subtract 40, giving 8. Japan 8 is 15.3 mm inside, 0.01 mm larger than a US 4½, so Japanese 8 is the nearest match.

Quarter sizes either side

A 4¼ is 15.08 mm and a 4¾ is 15.49 mm, each about 0.2 mm from a 4½: roughly the thickness of two sheets of paper on the diameter. If your ring falls between 4¼ and 4¾ on the 1:1 circle, order a 4½ for a band under 4 mm.

For a 4–6 mm band, jewellers suggest 4¾ to 5; for 7 mm and wider, 5 to 5½; for a comfort-fit inside, 4 to 4¼. Smart-ring kits that include a size 5 sample: Oura Ring 4. Galaxy Ring and Ring AIR do not reach it.

Making a size 4½ band

The blank length is the circumference of the middle of the band wall: π × (15.29 + thickness). Cut 52.7 mm of 1.5 mm stock or 54.3 mm of 2.0 mm stock, and the finished band has an outside diameter of 18.29 or 19.29 mm. Leave a little extra for filing the joint, and true the band on a mandrel at 4½ after soldering.

Blank = π × (15.29 mm + t) · 1.5 mm → 52.7 mm · 2.0 mm → 54.3 mm

Questions

Answered plainly.

01What is a size 4½ ring in mm?+

A US size 4½ ring is 15.29 mm (0.602") across the inside, with an inside circumference of 48.0 mm (1.89").

02What is a US size 4½ in UK and EU sizes?+

US 4½ is UK I½ and EU (ISO 8653) 48. It is also Japan 8 and Swiss 8.

03How much bigger is a size 5 than a size 4½?+

A size 5 is 0.41 mm wider inside (15.69 against 15.29 mm) and 1.28 mm longer round.

04How long a blank do I cut for a size 4½ ring?+

52.7 mm for 1.5 mm thick stock and 54.3 mm for 2.0 mm, from π × (15.29 mm + thickness).

05Should I order a size 4½ for a wide band?+

For a band 7 mm or wider, jewellers suggest 5 to 5½; for 4–6 mm, 4¾ to 5. Under 4 mm, a 4½ fits true to size.

Ring sizesUS · inside Ø mm

Carat sizes

Necklace lengths