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EU to US Ring Size Converter

Convert ring sizes between the US, UK, EU/ISO and Japanese systems, or start from a measured diameter or circumference in millimetres.

How to measure at home

No ring at hand: wrap a thin strip of paper or a thread snugly around the base of the finger, mark where it overlaps and measure the length in mm — that is the circumference. Fingers swell during the day, so measure in the evening at room temperature.

With a ring that fits: measure the inner diameter of the ring in mm from edge to edge across the centre, then convert from “Inner diameter, mm”. Pick a ring worn on the same finger of the same hand.

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Reading the size
Matching the ISO 8653 table
Building the conversion

Result

This page opens the ring size converter preset for the opposite of the usual direction: from a European size to the US & Canada number. Enter an EU size like 52, 54 or 56.5 and the tool returns the closest American size in quarter-size precision, plus the whole matching row across UK, Japan and millimetres.

European and ISO 8653 sizes are the inner circumference in millimetres, which makes them easy to measure but unfamiliar to American shops. EU 52 sits near US 6, EU 54 near US 6¾–7, and EU 57 near US 8 — in-between values are interpolated linearly, so 54.4 does not get silently rounded before converting.

Use this preset when your size was taken by a European jeweller and you are ordering from a US or Canadian store. American sizes come in quarter steps, so if the converted value falls between catalogue sizes, size up rather than down.

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Accepted Formats & Rules

  • ISO 8653 based conversion table with 44 standard sizes.
  • Accepts UK letter sizes including halves, like M or M½.
  • Millimetre inputs are interpolated between table rows for an exact match.

Key Benefits

✓ Convert between five sizing systems and raw millimetre measurements in one place.
✓ See the full matching row at once — US, UK, EU/ISO, Japan, diameter and circumference.
✓ Includes simple instructions for measuring your finger or an existing ring at home.

Use Cases

  • • Convert a ring size from an American online store to the EU size your local jeweller uses.
  • • Find your own size by measuring an existing ring's inner diameter or your finger's circumference.
  • • Check a UK letter size like M½ against the US, European and Japanese scales before ordering a gift.