Ring Size Converter

Ring Size Converter

The listing says US 7 or UK N — what's your size? Wrap a strip of paper around your finger, enter the circumference in millimetres or any size you know, and get US, UK, Japanese sizes and the inner diameter.

Runs in your browser — nothing you enter is uploaded

I know my

Size

Inner circumference (mm, EU / ISO 8653): 52 mm
Inner diameter (mm): 16.55 mm
US / Canada: 6
UK / Australia: L½
Japan: 12

Ring size chart

US / Canada	UK / Australia	Japan	Inner circumference (mm, EU / ISO 8653)	Inner diameter (mm)
3	F½	4	44.2	14.07
3.5	G½	5	45.47	14.47
4	H½	7	46.75	14.88
4.5	I½	8	48.03	15.29
5	J½	9	49.3	15.69
5.5	K½	10	50.58	16.1
6	L½	12	51.86	16.51
6.5	M½	13	53.13	16.91
7	N½	14	54.41	17.32
7.5	O½	15	55.69	17.73
8	P½	16	56.96	18.13
8.5	Q½	18	58.24	18.54
9	R½	19	59.52	18.95
9.5	S½	20	60.79	19.35
10	T½	21	62.07	19.76
10.5	U½	22	63.35	20.16
11	V½	24	64.63	20.57
11.5	W½	25	65.9	20.98
12	X½	26	67.18	21.38
12.5	Z	27	68.46	21.79
13	Z+1	29	69.73	22.2

Printable ring sizer

Print at 100% / “Actual size”, not “Fit to page”, and check the 50 mm line with a ruler. Lay a ring that fits on the circles: the right size is the circle whose line just shows along the inside of the ring. Or cut out the strip, wrap it around the finger and read the size where it meets the 0 line.

To measure: wrap a strip of paper around the finger, mark where it overlaps and measure the length in mm — that is the inner circumference. Or measure the inside of a ring that fits.

US sizes use diameter = 11.63 + 0.8128 × size; UK letters step about 1.25 mm in circumference from A ≈ 37.5 mm; Japan sizes step ⅓ mm in diameter from 13 mm. Jewellers’ charts differ slightly, so confirm with the shop’s ring sizer for expensive rings.

How to use

Measure your finger with a paper strip, or the inside diameter of a ring that fits.
Choose what you measured or know and enter the value.
Read the sizes; open the chart for more.
No ruler? Download the printable ring sizer, print it at 100% and match a ring to the circles or use the cut-out strip.

Options explained

European sizes: Per ISO 8653, the size is the inner circumference in millimetres — size 52 is 52 mm around.
US, UK and Japan: US diameter = 11.63 + 0.8128 × size; UK letters differ by about 1.25 mm of circumference; Japanese sizes by about ⅓ mm of diameter.

Worked example and formulas

Everything is converted through the inner diameter, and the circumference is that diameter × π. Say you measure a paper strip at 52 mm. The inner diameter is 52 ÷ π = 16.55 mm, and the other sizes follow:

System	Formula	For 52 mm
US / Canada	(diameter − 11.63) ÷ 0.8128	6
UK / Australia	(circumference − 37.5) ÷ 1.25 letter steps, with A at 37.5 mm	L½
Japan	(diameter − 13) × 3 + 1	12

Whole US sizes in the same chart:

US	Inner circumference	Inner diameter	UK	Japan
5	49.3 mm	15.69 mm	J½	9
6	51.9 mm	16.51 mm	L½	12
7	54.4 mm	17.32 mm	N½	14
8	57.0 mm	18.13 mm	P½	16
9	59.5 mm	18.95 mm	R½	19
10	62.1 mm	19.76 mm	T½	21

US sizes are shown to the nearest quarter and UK letters to the nearest half letter. The converter accepts inner diameters from about 10 to 26 mm.

Frequently asked questions

I'm between two sizes.

Usually choose the larger one, and make sure it passes over the knuckle. Fingers are slightly smaller when cold.

Why does another chart differ slightly?

Jewellers' charts vary, usually by less than half a size. For expensive rings, confirm with the shop's ring sizer.

Is the paper strip method accurate?

Fairly, if the strip is snug but not tight and doesn't stretch. Measure two or three times.

How do I use the printable ring sizer?

Print the PDF at 100% (Actual size) and check that the 50 mm line really measures 50 mm. Put a ring that fits on the circles — the right circle's line just shows along the inside of the ring — or cut out the strip, wrap it around your finger and read the size at the 0 line.

Privacy

This tool runs entirely in your browser. Your files and text are processed on your device and are never uploaded to our servers.