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The most common women's ring size in the US is 6 to 6½ — roughly 16.5mm to 16.9mm inner diameter, equivalent to UK L½–M½ and European 51¾–53. Average finger size varies with overall frame, so this is a starting point, not a rule. A woman with smaller hands typically measures US 4–5½, and a woman with larger hands measures US 7½–9. For a surprise engagement ring, never assume an average — measure a ring she already wears.

The most common men's ring size in the US is 9 to 10½ — roughly 18.9mm to 20.2mm inner diameter, or UK R½–U½ and European 59¼–63. Wide men's wedding bands usually require going up a quarter size from a thin band measurement. If you're sizing for a tungsten or Damascus steel band, that adjustment matters — these metals can't be resized.

UK ring sizes use letters (A through Z, plus Z+1 and Z+2 for the largest sizes), while US sizes use numbers (3 through 13½). A US 6 is UK L½, a US 7 is UK N½, a US 8 is UK P½, and a US 9 is UK R½. When ordering from a US jeweler in the UK, give your inner diameter in millimitres as a backup — it removes any chance of a letter/number conversion error.

European ring sizes are simply the inner circumference of the ring in millimetres. A European 54 means the ring measures 54mm around the inside — which corresponds to a US 7 and a UK N½. European 57 is US 8, European 60½ is US 9½, and European 63 is US 10½. Because the European system uses direct measurement in whole millimeters, you may occasionally see half-millimeter sizes (54¼, 55½) when a jeweler is converting from another system.

Yes, for most rings. Solid gold and platinum rings can typically be resized up to two sizes in either direction. Sterling silver and gold vermeil can usually be resized within a narrower range, and tungsten, titanium, Damascus steel, and fully stone-set eternity bands cannot be resized at all. Resizing fees at Aquamarise start from $65 depending on material.

For U.S. orders, Aquamarise® offers one complimentary size exchange on eligible designs, provided the ring is not customized or engraved. This allows you to shop with confidence, even when purchasing a surprise gift.

Customized or engraved items are final sale and not eligible for size exchanges. Alterations are available. For full details and eligibility requirements, please review our Care & Warranty Policy or contact our team before placing your order.

Wrap a thin paper strip or non-stretchy string around the base of the finger, mark where the ends meet, and measure the length in millimetres against a ruler. That number is your finger's circumference — a US 6 is 51.9mm; a US 8 is 57.0mm. Take the measurement at the end of the day and repeat it twice for accuracy. Alternatively, lay a ring that already fits on a ruler and measure the inner diameter in millimetres — this is more accurate than string.

Yes. Aquamarise® uses U.S. sizing, but the conversion chart above is available for many countries’ sizes.

Yes. Fingers may swell slightly in the afternoon or after activity. Measuring at the end of the day provides the most accurate result.

Trace the inner circle of a ring they already wear or press it into a bar of soap to capture the shape. Compare the imprint to the Aquamarise® size chart.

Yes. A wide band (6mm or wider) sits against more skin and feels significantly tighter than a thin band of the same nominal size. For men's wedding bands in the 6–8mm range, size up by a quarter to half size. For the widest styles — 8mm+ — size up by a half size. If possible, try on a sample band in the exact width you plan to order before committing to a size.