Buying Guides

Ring Size Guide

Measure once, order right. Two reliable ways to find a ring size at home, plus a full international conversion chart across US, UK, EU and millimetre standards.

6 min readUpdated July 19, 2026

Getting it right the first time

Ring size is the single most common cause of a returned order. It is also the easiest thing to get right, provided you measure the correct finger, at the correct time of day, with a method that does not stretch.

Every ring size ultimately expresses one measurement: the inside circumference of the band in millimetres. US, UK and EU systems are just different labels for the same underlying figure, which is why the conversion chart below is exact rather than approximate.

Two reliable ways to measure at home

Method 1 — measure the finger

1
Cut a strip of paper or take a length of string
Roughly 6 mm wide and long enough to wrap around comfortably. Avoid elastic or anything that stretches — it will read small.
2
Wrap it around the base of the finger
Snug, not tight. It must be loose enough to slide back over the knuckle, because that is what the finished ring will have to do.
3
Mark the overlap and measure it flat
Mark exactly where the end meets the strip, lay it against a ruler and read the length in millimetres. That figure is your inside circumference.
4
Match it to the chart
Find your circumference in the table below and read across for the US, UK and EU equivalents.

Method 2 — measure a ring that already fits

Take a ring already worn on the intended finger and measure the inside diameter across the widest point, in millimetres. Match that diameter in the chart. This is usually the more accurate of the two methods, provided the reference ring genuinely fits well.

International ring size conversion chart

Diameter and circumference are the constants; the regional sizes are conventions mapped onto them. Where a size falls between two rows, take the larger.

US / Canada	UK / Australia	EU	Diameter (mm)	Circumference (mm)
3	F	44	14.1	44.2
3½	G	45½	14.5	45.5
4	H	47	14.9	46.8
4½	I	48	15.3	48.0
5	J½	49	15.7	49.3
5½	L	50	16.1	50.6
6	M	52	16.5	51.9
6½	N	53	16.9	53.1
7	O	54	17.3	54.4
7½	P	56	17.7	55.7
8	Q	57	18.1	57.0
8½	R	58	18.5	58.3
9	S	59	18.9	59.5
9½	T	61	19.4	60.8
10	U	62	19.8	62.1
10½	V	63	20.2	63.4
11	W	65	20.6	64.6
12	Y	67	21.4	67.2

Values are industry-standard conversions. Minor variation of ±0.1 mm exists between manufacturers.

Band width changes the fit

A wide band contacts more of the finger and feels tighter than a narrow band of the same nominal size. As a working rule, for bands of roughly 6 mm and wider, go up a quarter to a half size. For very narrow bands under 2 mm, stay at your measured size.

Band width	Adjustment	Typical use
Under 2 mm	No change	Stacking and eternity bands
2–5 mm	No change	Most engagement and dress rings
6–8 mm	Up ¼ to ½ size	Men's wedding bands
Over 8 mm	Up ½ size	Heavy signet and statement rings

A practical starting point — confirm with a physical sizer in the intended width where possible.

What can and cannot be resized

Most plain and simple-set bands in gold or silver can be taken up or down by a size or two by a competent bench jeweller. Some designs cannot be altered at all and must be manufactured to the correct size from the outset:

Design	Resizable?	Note
Plain band	Yes	Straightforward, one to two sizes
Solitaire with plain shank	Yes	Standard workshop job
Partially set shank	Limited	Only the unset portion can be worked
Full eternity band	No	Must be remade to size
Tension setting	No	Resizing compromises the stone's security
Patterned or milgrain shank	No	The pattern cannot be reconstructed

Frequently asked questions

How do I measure my ring size at home?

Wrap a strip of paper or a length of string snugly around the base of the finger, mark where it overlaps, and measure the length in millimetres. That figure is your inside circumference — match it to the chart to find your size. Alternatively, measure the inside diameter of a ring that already fits.

What time of day should I measure my ring size?

Late afternoon or evening. Fingers are at their smallest in the morning and in cold weather, and swell slightly through the day and in heat. Measuring at the end of the day gives a size that stays comfortable rather than tight.

Should a wide band be a different size?

Yes. Wide bands sit against more of the finger and feel tighter than a narrow band of the same size. For bands roughly 6 mm and wider, it is common to go up a quarter to a half size.

What if my size falls between two sizes?

Choose the larger size. A ring that is marginally loose can be sized down or fitted with a beading insert, whereas a ring that will not pass the knuckle cannot be worn at all.

Can a ring be resized after it is made?

Most plain and simple-set bands in gold and silver can be resized by a competent bench jeweller, usually within a size or two. Full eternity bands, tension settings and some patterned designs cannot be resized and must be remade to the correct size.

Wholesale & B2B

Buying certified diamonds for your business?

We manufacture IGI, GIA and HRD certified diamonds and custom gold jewelry for retailers and wholesalers worldwide.

Request wholesale pricing Browse products

Keep reading

More guides

Diamond Education

The 4 Cs of Diamonds

Cut, Colour, Clarity and Carat — the four grades that decide what a diamond looks like and what it costs. A visual guide to reading any certificate with confidence.