The International Ring Size Chart: A Complete Guide

Every country measures the same thing — the inside of the band — but each one labels it differently. Understanding what each label actually represents makes international ring shopping straightforward.

The systems at a glance

• United States and Canada: numeric, from about 3 to 13, in half and quarter steps.
• United Kingdom, Ireland, Australia and New Zealand: alphabetic, A to Z with half letters.
• European ISO standard: the inside circumference in millimetres, rounded to a whole number. A size 54 ring measures 54 mm around the inside.
• France: the ISO circumference minus 40. A French 14 is a 54 mm ring.
• Germany: the inside diameter in millimetres, so a German 17.3 is a 54 mm circumference.
• Switzerland: its own numeric scale, roughly the ISO circumference minus 39.5, in half steps.
• Japan and much of East Asia: a numeric scale from 1 to 27, advancing about 0.8 mm of circumference per size.
• Brazil: a numeric scale close to the ISO circumference minus 39.

Reading a chart without errors

Always find the millimetre column first. Circumference and diameter are the two neutral columns that every other system can be derived from, and they never disagree with themselves. Locate your known size, read across to millimetres, then read back out to the system you need.

Watch for charts that mix circumference and diameter in adjacent columns without labels. A 17.3 in a diameter column and a 54 in a circumference column are the same ring; a 17.3 read as a circumference would be a child's size.

Rounding conventions differ

European sizes are whole millimetres, so they are coarser than US quarter sizes. A US 6¾ and a US 7 can both map to EU 54. When converting from a fine scale to a coarse one, some precision is unavoidably lost. When converting from coarse to fine, choose the nearest available size and confirm the millimetre value with the seller.

Buying from another country

Ask three questions before ordering: what is the inside diameter in millimetres, how wide is the band, and is the ring resizable. Those three answers settle almost every fit problem. Wide bands run tight; non-resizable designs such as full eternity rings and tension settings must be right the first time.

A note on men's and women's sizes

There is no separate men's or women's scale anywhere in the world. The same numbers and letters apply to everyone. What differs is the typical range: most women's rings fall between US 5 and 8, most men's between US 8 and 12, but plenty of people sit outside those bands. Measure rather than assume.

Use the converter on the home page to move between all of these systems at once, and confirm the resulting millimetre figure against the ring or finger you measured.