Ring Size Converter: US, UK Letters, EU & Printable Sizer

A US ring size 7 is a UK N½ and an EU 54, with an inside diameter of about 17.3 mm, and a US 6 is a UK L½ and an EU 52. Use the ring size converter below to switch between US numbers, UK letters, EU, Japanese and millimetre sizes, or print the ring sizer to check a ring you already own.

I know myUS / Canada sizeUK / AU letterEU (ISO) sizeinside diameter (mm)finger circumference (mm)Size

Your conversion appears here. The full chart is below.

Print the ring sizer

Ring size conversion chart

US / Canada	UK / AU	EU (ISO)	Japan	Inside diameter	Inside circumference
3	F½	44	4	14.1 mm	44.2 mm
3½	G½	45	5	14.5 mm	45.4 mm
4	H½	47	7	14.9 mm	46.7 mm
4½	I½	48	8	15.3 mm	48 mm
5	J½	49	9	15.7 mm	49.3 mm
5½	K½	51	10	16.1 mm	50.5 mm
6	L½	52	11	16.5 mm	51.8 mm
6½	M½	53	13	16.9 mm	53.1 mm
7	N½	54	14	17.3 mm	54.4 mm
7½	O½	56	15	17.7 mm	55.6 mm
8	P½	57	16	18.1 mm	56.9 mm
8½	Q½	58	18	18.5 mm	58.2 mm
9	R½	59	19	18.9 mm	59.5 mm
9½	S½	61	20	19.3 mm	60.7 mm
10	T½	62	21	19.7 mm	62 mm
10½	U½	63	22	20.1 mm	63.3 mm
11	V½	65	24	20.5 mm	64.6 mm
11½	W½	66	25	21 mm	65.8 mm
12	X½	67	26	21.4 mm	67.1 mm
12½	Y½	68	27	21.8 mm	68.4 mm
13	Z½	70	29	22.2 mm	69.7 mm
13½	Z+1½	71	30	22.6 mm	70.9 mm

How to measure your ring size at home

The most accurate home method uses a ring that already fits the finger you are buying for. If you don’t have one, a strip of paper works as a backup.

With the printable ring sizer

1. Press the “Print the ring sizer” button under the converter. It prints a sheet of circles for US sizes 4 to 13.
2. In your print settings, choose 100% or “actual size”. Turn off “fit to page” or any scaling.
3. Before you use the sheet, measure the 50 mm line at the bottom with a ruler. It must be exactly 50 mm. If it isn’t, the circles are the wrong size too, so fix the print settings and print again.
4. Lay a ring that fits on the circles. The circle whose line matches the inside edge of the ring is your size.
5. If the ring falls between two circles, choose the larger one.

With a strip of paper

1. Cut a thin strip of paper that does not stretch.
2. Wrap it round the base of the finger, snug but not tight, and mark where it overlaps.
3. Lay the strip flat and measure from the end to the mark in millimetres. That is your finger circumference.
4. Choose “finger circumference (mm)” in the converter and pick the nearest value.
5. Check that a ring of that size would pass over your knuckle. If your knuckle is larger than the base of the finger, measure round the knuckle too and choose a size between the two readings.

Fingers are often slightly larger at the end of the day and in warm weather, so measure more than once if you can.

How the ring size systems compare

US and Canadian sizes are numbers in half-size steps. Each full size adds about 2.55 mm to the inside circumference, so a half size is a little under 1.3 mm.

UK and Australian sizes are letters. Size C is 40 mm round the inside, and each letter adds 1.25 mm, with half letters in between. Because the two scales step differently, whole US sizes land on UK half letters: US 7 is N½ and US 8 is P½.

EU sizes follow the ISO system, where the size is simply the inside circumference in millimetres. Japanese sizes are small whole numbers, with one size equal to about a third of a millimetre of inside diameter.

Wide bands, 6 mm and above, sit on more of the finger and usually need half a size larger than a thin band.

Quick answers

• US 5: UK J½, EU 49, 15.7 mm diameter
• US 6: UK L½, EU 52, 16.5 mm diameter
• US 7: UK N½, EU 54, 17.3 mm diameter
• US 8: UK P½, EU 57, 18.1 mm diameter
• US 9: UK R½, EU 59, 18.9 mm diameter
• US 10: UK T½, EU 62, 19.7 mm diameter
• US 11: UK V½, EU 65, 20.5 mm diameter

FAQs

What is a UK size L in US ring sizes?

A UK L has an inside circumference of about 51.25 mm. That falls between a US 5½ (UK K½) and a US 6 (UK L½), so it is roughly a US 5¾. If a brand only sells half sizes, try the US 6.

Are men’s and women’s ring sizes different?

No. Every system here is unisex, so a US 9 is the same size whoever wears it. What changes is the band: a wide band needs about half a size more than a thin one of the same size.

Can I measure my ring size with string?

You can, but string stretches and twists, which can give a reading that is too large. A paper strip, or a ring that fits on the printed sizer, is more reliable.

Why do the printed circles look the wrong size?

Your printer has almost certainly scaled the page. Check the 50 mm line with a ruler, set printing to 100% or actual size, and print again.

What does an EU ring size mean?

It is the inside circumference in millimetres. An EU 57 ring measures about 57 mm round the inside, which is a US 8.

If you are choosing a watch as well, the watch size calculator works from a wrist measurement taken in much the same way. You will find every converter in the size guide.

Ring sizes are calculated from published formulas. US and Canadian sizes use a straight-line fit to ISO 8653 between US size and inside circumference (C = 2.55 × US + 36.5 mm). UK and Australian letters start at C = 40 mm, with one letter per 1.25 mm. EU (ISO) sizes equal the inside circumference in millimetres, and Japanese sizes take size 1 as about 13 mm diameter with roughly one third of a millimetre per size. Figures are rounded, so a brand’s own chart may differ slightly.

Look up one size

US / Canada

• 3
• 3.5
• 4
• 4.5
• 5
• 5.5
• 6
• 6.5
• 7
• 7.5
• 8
• 8.5
• 9
• 9.5
• 10
• 10.5
• 11
• 11.5
• 12
• 12.5
• 13
• 13.5

UK / Australia

• F
• G
• H
• I
• J
• K
• L
• M
• N
• O
• P
• Q
• R
• S
• T
• U
• V
• W
• X
• Y
• Z