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Size charts

Ring size chart

A US size 7 ring has an inner diameter of 17.3 mm and an inner circumference of 54.4 mm. Each whole US size adds 0.8128 mm of diameter, and the international standard (ISO 8653) names a size by its inner circumference in millimetres, so US 7 is about EU 54. The chart below converts US sizes 3 to 13 to UK letters, EU/ISO, Japanese and Indian sizes, and the circles print at actual size.

Data checked October 5, 2026 against the sources listed below.

International ring size conversion

International ring size conversion

Diameter and circumference are the ring's inside measurements. EU/ISO is the inner circumference rounded to the nearest mm. ≈ marks Indian sizes where a US size falls between two Indian sizes (value from CaratLane's US-to-India table). Brands differ by about 0.1–0.2 mm; at US 13 some UK charts say Z+1.
US / CanadaInner diameterInner circumferenceUK / AustraliaEU / ISOJapanIndia
314.1 mm44.2 mmF444≈5
3.514.5 mm45.5 mmG455≈6
414.9 mm46.8 mmH477≈7
4.515.3 mm48.0 mmI4888
515.7 mm49.3 mmJ½499≈10
5.516.1 mm50.6 mmK½5110≈11
616.5 mm51.9 mmL½521212
6.516.9 mm53.1 mmM½531313
717.3 mm54.4 mmN½541414
7.517.7 mm55.7 mmO½5615≈16
818.1 mm57.0 mmP½571617
8.518.5 mm58.3 mmQ½581718
919.0 mm59.5 mmR½6018≈20
9.519.4 mm60.8 mmS½611921
1019.8 mm62.1 mmT½622022
10.520.2 mm63.4 mmU½6322≈23
1120.6 mm64.6 mmV½652325
11.521.0 mm65.9 mmW½662426
1221.4 mm67.2 mmX½672527
12.521.8 mm68.5 mmZ6826≈28
1322.2 mm69.7 mmZ½702730
Ring size chart showing actual-size circles for US ring sizes 4 to 12 with their inner diameters in millimetresUS 414.9 mmUS 515.7 mmUS 616.5 mmUS 717.3 mmUS 818.1 mmUS 919.0 mmUS 1019.8 mmUS 1120.6 mmUS 1221.4 mm50 mm: check with a ruler after printing at 100%
Printable at actual size: print this page at 100% scale (no "fit to page") and check the 50 mm bar with a ruler.

When to size up or down

SituationWhat to do
Wide band (from about 4 to 6 mm)Go up about 1/4 to 1/2 a size.
Very thin band (under 1.3 mm)Consider sizing down.
Comfort-fit bandCan run large; consider a half size smaller.
Large knuckleMeasure the knuckle and the base of the finger, then choose a size in between.
Time and temperatureFingers shrink when cold and swell when warm; measure later in the day at a normal temperature.
Between two sizesChoose the larger size.

How to measure

  1. 1

    Wrap a string or paper strip

    Use something that does not stretch. Wrap it around the base of the finger you will wear the ring on, snug but not tight, and mark where the ends meet.

  2. 2

    Measure it in millimetres

    Lay it flat against a ruler. That length is your inner circumference: find it in the chart, or divide it by 3.14 to get the inner diameter.

  3. 3

    Or measure a ring that fits

    Lay a millimetre ruler across the inside of a ring that fits the same finger, edge to edge. That is the inner diameter.

  4. 4

    Or use the circles on this page

    Print at 100% scale (no fit-to-page) and check the 50 mm bar with a ruler. Place your ring over the circles until its inner edge lines up with one.

  5. 5

    Measure at the right time

    Fingers are smaller when cold and larger when warm, so measure later in the day at a normal temperature. If you fall between two sizes, choose the larger one.

How ring sizes convert between countries

ISO 8653 defines a ring size by its inner circumference in millimetres. US and Canadian sizes rise in steps of 0.032 inches (0.8128 mm) of diameter per whole size, so the two scales line up through a simple formula: inner diameter (mm) = 0.8128 × US size + 11.63.

The UK, Ireland and Australia use letters with half sizes; under BS 6820 each letter adds 1.25 mm of circumference, with C at 40 mm. Italy, Spain and Switzerland quote the circumference minus 40, so their size 10 is ISO 50. Japan and India use whole-number scales that are not linear in millimetres, which is why the last two columns are the ones most often printed differently from brand to brand.

Frequently asked questions

For women, sizes 5 to 7 are most common and US 6 is the most popular. For men, sizes 8 to 10.5 are most common and US 9 is the most popular.

A US size 7 ring has an inner diameter of about 17.3 mm and an inner circumference of 54.4 mm, which is about EU/ISO 54, UK N½ and Japan 14.

Find your US size in the chart and read across: US 6 is UK L½, US 7 is UK N½ and US 8 is UK P½. Each UK letter adds 1.25 mm of inner circumference.

Usually yes. A wide band feels tighter than a thin one in the same size, so retailers suggest going up about a quarter to half a size for bands wider than roughly 4 to 6 mm.

Accurate if it prints at true scale. Set page scaling to 100% (or None) and check the 50 mm bar against a real ruler before you use the circles.

Use this chart on your site or listing

Free to embed or print, as long as the credit link to Hues AI stays with it. Copy the code:

Ring size chart showing actual-size circles for US ring sizes 4 to 12 with their inner diameters in millimetres

Sources

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