Ring Size Calculator

Ring shopping across borders — or surprise-gift shopping across a partner's jewelry box — runs into three incompatible labels for the same finger: a US 7, a UK N½, and an EU 54 are the same ring. The confusion is pure convention; underneath is one number in millimeters.

Convert from any starting point: the US size on a receipt, a diameter measured across an existing ring, or a circumference from a string test. You get all systems plus the physical measurements — the part worth writing down for future purchases.

The other sizing puzzle — feet — lives in the Shoe Size Converter

One measurement, three labels:

Worked example: US 7 → 17.3 mm diameter → 54.4 mm circumference → EU 54, UK N½. The EU system's honesty is worth copying: it just says the measurement.

The common range — every row computed by this calculator's formulas:

UK letters between brands drift by a half step — when a letter matters (UK purchase), confirm against the mm circumference, which never lies.

Two reliable home methods, in order of trustworthiness:

• Existing ring + ruler: measure the INSIDE diameter edge-to-edge in mm and enter it above — the best method, since the ring already fits.
• String or paper strip: wrap snugly where the ring sits, mark the overlap, measure the length in mm — that's the circumference (enter directly). Repeat twice; string stretch causes overshoot.
• Measure in the evening — fingers run smaller in the morning and in cold; knuckle-dominant fingers should size to pass the knuckle comfortably.
• Between sizes: go up for wide bands (they wear tighter), stay true for thin bands.
• Surprise shopping: borrow a ring she wears on the SAME finger of the same hand — other fingers differ by multiple sizes.

Free jeweler sizing exists almost everywhere — use it before resizing anything sentimental; resizing has limits, especially with stones around the band.