18 mm ring size

The 18 mm ring size, measured straight across the inside, is about a US 7¾. In the UK it is P, and in Europe 56, and the ring is 56.5 mm round the inside.

18 mm ring size in every system

18 mm ring size: every system
US and Canada	about 7¾
UK, Ireland, Australia	P
Europe (EU)	56
Japan and China	15 to 16
India	16
Italy, Spain, Switzerland	16
Across the inside	18.0 mm · 1.80 cm · 0.709 in
Around the inside	56.5 mm · 5.7 cm · 2.23 in

Every half millimetre is a little over half a US size, so a 17.5 mm or 18.5 mm ring is the next size down or up. All of these numbers are from the standard ring size conversion table.

See a 18 mm ring at its real size

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

US7¾

UK P · EU 56 · Japan 15 to 16 · India 16

18.0 mm (0.71 in) across the inside · 56.5 mm (2.23 in) around

Between US 7½ and 8? Choose 8, the bigger one, especially for a wide band.

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)
6¾	N	54	17.1	53.8
7	N½	54	17.3	54.4
7¼	O	55	17.5	55.1
7½	O½	56	17.7	55.7
7¾	P	56	17.9	56.3
8	P½	57	18.1	57.0
8¼	Q	58	18.3	57.6
8½	Q½	58	18.5	58.3
8¾	R	59	18.8	58.9

Your questions on a 18 mm ring

How long is the inside of a 18 mm ring, measured all the way round?

Round the inside it is 56.5 mm, which is 5.7 cm. Straight across, it is 0.71 inches.

Which US ring size matches 18 mm across?

It is close to a US 7¾. In the UK that ring is P, and in Europe 56.