Ring size 5.5 in mm, cm, UK and EU

Ring size 5½ in the US means a ring 16.1 mm wide inside and 50.6 mm round. The UK calls the same ring K½, Europe 51, Japan 10 and India 10 to 11.

Ring size 5.5 in every system

Ring size 5.5 in mm, cm, UK and EU: every system
US and Canada	5½
UK, Ireland, Australia	K½
Europe (EU)	51
Japan and China	10
India	10 to 11
Italy, Spain, Switzerland	11
Across the inside	16.1 mm · 1.61 cm · 0.634 in
Around the inside	50.6 mm · 5.1 cm · 1.99 in

One whole size bigger, US 6½, is just under 1 mm wider. All of these numbers are from the standard ring size conversion table.

Check a ring against ring size 5.5 on your screen

1Match a bank card

The card works like a ruler: nothing on it is read or saved, and a driving licence works too. Only its height counts, so the drawing may run off the edge of a phone. Hold the card flat on the screen, long side across, with its top edge on the drawing's top line. Then move the slider until the drawing's bottom line meets the card's bottom edge.

Optional. Only needed to lay a ring or strip on the screen; typed measurements work without it. Nothing on the card is read or saved.

2Measure

A ring I own My finger Print a sizer

Inside diameter of your ring mm

Lay the ring on the circle, or type the inside diameter if you measured it.

Length of your paper strip mm

Wrap a thin strip of paper around the base of your finger, mark where it overlaps, then measure to the mark.

The circle shows a 17.3 mm ring, drawn for a typical screen.

This size, drawn on your screen

US5½

UK K½ · EU 51 · Japan 10 · India 10 to 11

16.1 mm (0.63 in) across the inside · 50.6 mm (1.99 in) around

For a wide band (over 4 mm), go up about half a size, to US 6.

See every size in the ring size chart · Convert a size you already know

Nearby sizes

Too tight or too loose? Try the size one row up or one row down.

Nearby sizes
US and Canada	UK and Australia	Europe (EU)	Inside diameter (mm)	Circumference (mm)
4½	I	48	15.3	48.0
4¾	J	49	15.5	48.7
5	J½	49	15.7	49.3
5¼	K	50	15.9	50.0
5½	K½	51	16.1	50.6
5¾	L	51	16.3	51.2
6	L½	52	16.5	51.9
6¼	M	52	16.7	52.5
6½	M½	53	16.9	53.1

Common questions about ring size 5.5

How many millimetres is US ring size 5½?

It is 16.1 mm wide inside and 50.6 mm round the inside. In inches, the width is 0.63.

How many centimetres is US ring size 5½?

Round the inside it is 5.1 cm, and it is 1.61 cm wide.