This free ring size chart helps you find your ring size in seconds — convert between US, UK, European and Japanese sizes, measure your ring size at home, or size from a ring you already own. Use the interactive finder below, or read the full ring size chart and step-by-step measuring guide underneath.

Find your ring size

Enter a size to convert it across every system, measure the inside diameter of a ring that fits, or measure your finger — the tool returns your US, UK/Australian, European (ISO) and Japanese size instantly.

Know your size already?

Pick the system and size you know — we'll show every equivalent.

Sizing system

Your size

Your ring size

US / Canada

N½

UK / AU

Europe (ISO)

Japan

17.3

Diameter mm

54.4

Circumference mm

Print-at-home ring sizer

The easiest, most accurate way to size at home — print our ready-made gauge and read your size straight off it. No maths, no re-typing.

⇩ Download the printable ring sizer (PDF)

Print at 100% / “Actual size.” In your print dialog set Scale to 100% — not “Fit to page” or “Shrink to fit,” which stretches or shrinks the gauge.
Check the scale. Measure the printed ruler: it should be exactly 100 mm (10 cm). No ruler? Line a credit card up with the 85.6 mm marker. If it’s off, reprint at 100%.
Cut out the strip along the dashed outline, and snip the small slot.
Wrap it around the base of your finger, printed side out. Thread the pointed tip through the slot and pull snug — comfortable, not tight.
Read the number at the slot: the bold figure is your US ring size (the small number is your finger’s circumference in mm).

Tip: measure at the end of the day when fingers are warmest. Between sizes? Go up. Wide bands fit tighter — size up a half.

No printer? Measure by hand

You can still size with a strip of paper — the key is measuring accurately, so calibrate against something of a known size first.

85.6 mm wide

Any standard bank or credit card is exactly 85.6 mm wide. Hold one against your ruler or a printed page to confirm your scale is true to size before you measure — a printer set to "fit to page" can distort the result.

To measure your finger: cut a thin strip of paper about 6 mm wide, wrap it snugly around the base of the finger, mark where it overlaps, then lay it flat and measure to the mark in millimetres. That length is your circumference — enter it in the Measure finger tab above.

To measure a ring you own: place the ring on the ruler and measure straight across the inside opening, edge to edge. That's the diameter — enter it in the I have a ring tab above.

Measure warm, not cold

Fingers shrink in the cold and swell in heat. Size at the end of the day, at room temperature, for the truest everyday fit.

Mind the knuckle

The ring has to slide over your knuckle. If the knuckle is much larger than the base, size to a point in between.

Wide bands sit tighter

A band 6 mm or wider feels snugger than a thin one. For a wide or comfort-fit ring, consider sizing up by a quarter to a half size.

Measure more than once

Take two or three readings on different occasions and use the average. A single reading can mislead by a full size.

Full ring size conversion chart

Standard international ring size conversions
US / CA	UK / AU	EU (ISO)	Japan	Diameter (mm)	Circ. (mm)

Methodology & sources

Sizes are mapped from inside circumference, the measure shared by all international standards. US/Canada sizes follow the standard scale of quarter-size increments; European (ISO 8653) size equals the inside circumference in millimetres; UK/Australia uses the alphabetical scale; Japanese sizes follow the JIS official-size chart. Diameter is derived from circumference as circumference ÷ π.

When you measure by diameter or circumference, the tool returns the nearest standard size and flags when a measurement falls between two sizes so you can choose the better fit for your band width and knuckle. Conversions are rounded to the nearest published size and are intended as an accurate starting point, not a substitute for professional sizing.

Cite this tool

Free to reference. Please credit Diamond & Sapphire with a link.

Diamond & Sapphire, "Ring Size Chart & Finder," diamondandsapphire.com/pages/ring-size-chart

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Ring size chart (US, UK, EU & Japan)

Find your ring size by matching the inside circumference or diameter of a well-fitting ring (in millimetres) to the row below.

US / Canada	UK / Australia	Europe (ISO)	Japan	Circumference (mm)	Diameter (mm)
3	F½	44	4	44.2	14.1
4	H½	47	7	46.8	14.9
5	J½	49	9	49.3	15.7
6	L½	52	12	51.9	16.5
7	N½	54	14	54.4	17.3
8	P½	57	16	56.9	18.1
9	R½	59	18	59.5	18.9
10	T½	62	20	62.1	19.8
11	V½	64	22	64.6	20.6
12	Y	67	24	67.2	21.4
13	Z+1	69	26	69.7	22.2

How to measure your ring size at home

You don’t need special tools — just follow these steps, or download our printable ring sizer (PDF) and print it at 100% (Actual Size).

From a ring you own: pick a ring that fits the right finger, measure straight across the inside opening in millimetres — that’s the diameter — and match it to the chart above.
From your finger: wrap a thin strip of paper or string snugly around the base of the finger, mark where it overlaps, then measure the length in millimetres. That’s the circumference — find it in the chart.
With the printable sizer: print at 100%, verify the scale against the ruler on the page (it should read exactly 100 mm) or a credit card (85.6 mm wide), cut out the strip, wrap it around your finger, thread the tip through the slot, and read your size.

Ring sizing tips

Measure at the end of the day when fingers are warmest and largest, and avoid measuring when your hands are cold. Take two or three readings and use the average — a single reading can be off by a full size. If you’re between sizes, choose the larger. Wide or comfort-fit bands (6 mm or more) sit tighter, so size up about a half size. Remember the ring must slide over your knuckle: if your knuckle is much larger than the base of your finger, size to a point in between.

Ring Size Chart FAQ

How do I measure my ring size at home? Measure the inside diameter (in mm) of a ring that already fits and match it to the ring size chart above, or wrap paper/string around your finger to get the circumference. Our printable sizer makes it exact.

What is the most common ring size? For women, US sizes 6–6.5 are most common; for men, US 9–10. These are averages — always measure to be sure.

What is a US size 7 in UK and EU? A US 7 is roughly a UK N½ and a European (ISO) 54, with an inside circumference of about 54.4 mm.

How can I measure ring size without a sizer? Wrap a strip of paper or string around the base of your finger, mark the overlap, measure the length in millimetres, and match that circumference to the chart.

Is the printable ring size chart accurate? Yes — as long as you print at 100% (Actual Size) and confirm the scale using the on-page 100 mm ruler or a credit card before measuring.

Know your size? Explore our fine jewelry, or learn about every sapphire color before you choose.

Ring Size Chart