What is a UK size U ring in US sizes?

US 10.5. On the GIA chart a UK U is 63.5mm around the inside, which is the same row as US 10.5.

How many millimetres is ring size U?

63.5mm around the inside and 20.2mm across. European and ISO sizes are the circumference rounded to the millimetre, so it is a 64.

What is between size U and size V?

U½, at 64.1mm. Each half size adds about 0.6mm to the circumference and each full letter about 1.2mm, which is why a ring that is close but not right is usually a half size out rather than a whole one.

Is U a small or a large ring size?

It sits towards the larger end of the A to Z scale. A size is a measurement rather than a judgement, and the only way to know it is to measure the finger the ring is for.

Should I size up for a wide band in size U?

Often by a half size. A wide band covers more of the finger, so it can feel snugger than a narrow ring at the same marked size. Measure with a gauge close to the width you are buying, and our size finder explains how.

Ring sizes

UK ring size U

A UK U is a US 10.5 and an EU 64: 63.5mm around the inside of the ring and 20.2mm across it.

US and Canada: 10.5
EU and ISO: 64
Circumference: 63.5mm
Diameter: 20.2mm
Japan and Asia: 22
Switzerland: 22¾

Size U and the half sizes either side

UK sizes go up in half letters, each about 0.6mm around. If U is nearly right, the answer is usually the half size next to it rather than a whole letter away.

UK U with its neighbours, from the GIA conversion chart
UK	US	EU / ISO	Circumference	Diameter
T	10	62	62.2mm	19.8mm
T½	10.25	63	62.8mm	20mm
U	10.5	64	63.5mm	20.2mm
U½	10.75	64	64.1mm	20.4mm
V	11	65	64.7mm	20.6mm

What a band weighs in size U

A bigger size takes more metal, so the same ring weighs a little more in a larger size. These are the weights of a plain court band at 63.5mm, the inside of a size U, at four widths.

Estimated grams, plain court band, UK U, 1.6mm wall
Metal	2mm	4mm	6mm	8mm
Titanium	0.8g	1.7g	2.5g	3.4g
Zirconium	1.2g	2.5g	3.7g	4.9g
9ct yellow gold	2.1g	4.3g	6.4g	8.6g
18ct yellow gold	3.0g	5.9g	8.9g	11.8g
Platinum 950	3.8g	7.6g	11.4g	15.2g

Estimates from the model in our ring weight calculator, using the same reference alloys. A finished ring with a pattern, stone or different wall thickness will differ.

Rings made in size U

All 99 of our wedding bands are made to order in size U, in every width and finish they come in. Size is chosen on the ring's page, and if you are not sure yet you can order with "I do not know yet" and we confirm it with you before anything is made. The diamond solitaires are set in UK F to T, so a size U engagement ring is not one we can make.

Wedding rings · Engagement rings · Find your size at home · Finding a size secretly

Size U questions

What is a UK size U ring in US sizes?: US 10.5. On the GIA chart a UK U is 63.5mm around the inside, which is the same row as US 10.5.
How many millimetres is ring size U?: 63.5mm around the inside and 20.2mm across. European and ISO sizes are the circumference rounded to the millimetre, so it is a 64.
What is between size U and size V?: U½, at 64.1mm. Each half size adds about 0.6mm to the circumference and each full letter about 1.2mm, which is why a ring that is close but not right is usually a half size out rather than a whole one.
Is U a small or a large ring size?: It sits towards the larger end of the A to Z scale. A size is a measurement rather than a judgement, and the only way to know it is to measure the finger the ring is for.
Should I size up for a wide band in size U?: Often by a half size. A wide band covers more of the finger, so it can feel snugger than a narrow ring at the same marked size. Measure with a gauge close to the width you are buying, and our size finder explains how.