Convert any US ring size number to UK ring size letter instantly — full US to UK ring size conversion chart including all half sizes, bidirectional calculator, EU and MM reference, and expert tips updated for 2026
The six most important US-to-UK ring size conversion reference points are shown above. The universal women's anchor is US 6½ = UK N (53.8mm circumference, 17.1mm diameter, EU 54). The men's anchor is US 8 = UK Q (57.6mm circumference, 18.3mm diameter, EU 58). The key pattern to remember is that each full US size step equals approximately two UK letter steps and approximately 2.5mm of circumference — so US 6 = UK M, US 7 = UK O, US 8 = UK Q, US 9 = UK S. US half-sizes (US 6½, US 7½) fall between the UK full-letter equivalents and correspond to UK half-sizes.
| 🇺🇸 US Size | 🇬🇧 UK Size | 🇪🇺 EU / French | 📏 Circ MM | 📐 Diam MM | 📏 Circ CM | 🇯🇵 Japanese | 🇨🇭 Swiss |
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Before converting, confirm whether your US size is a whole number (US 6, US 7, US 8) or a half-size (US 6½, US 7½, US 8½). US half-sizes are extremely common — many people know their US size as "6 and a half" or "7 and a half" and these convert to different UK letters than the whole-number sizes. US 6 = UK M, but US 6½ = UK N — a full UK letter difference. Never assume a whole US number if your known size includes a half; enter the exact US size including the ½ into the calculator or lookup table above.
Enter your US size into the calculator and click Convert for an instant result showing UK, EU, MM circumference, MM diameter, Japanese, Swiss, and CM. Alternatively, find your US size in the left column of the full conversion chart and read across to the UK column. Every US half-size from US 1 to US 15 is included in the chart. The result in the UK column is your UK ring size letter — this is the size to enter on a UK retailer's order form.
Cross-check your US-to-UK conversion result using the EU and MM columns. The EU size should approximately equal the circumference in mm (EU size = mm circumference). If US 6½ gives UK N and EU 54, confirm that the MM column shows approximately 53.8mm — EU 54 ≈ 54mm ≈ 53.8mm. If these three readings are consistent, the conversion is correct. This three-way cross-check (US → UK → EU → MM) eliminates lookup errors and is the professional approach used by UK jewellers when verifying international size conversions from US retail sizing charts.
Some US sizes convert to a circumference that falls almost exactly between two adjacent UK letters. For example, US 5¾ (approximately 53.5mm) falls between UK N (53.8mm) and UK M½ (53.1mm). In this situation, always order the larger UK letter — UK N. A ring half a UK letter too large is immediately wearable, passes comfortably over the knuckle, and can be resized down at most UK jewellers free of charge. A ring half a UK letter too small is uncomfortable on the knuckle and requires professional resizing before it can be worn daily.
Both the US and UK systems include half-sizes, but they do not align perfectly. Each US half-size step equals approximately 1.25mm of circumference — the same as each UK half-size step. This means US half-sizes and UK half-sizes are the same physical increment in mm and map directly onto each other. US 6 = UK M, US 6½ = UK N, US 7 = UK O — each US whole-number maps to a UK letter that is two full UK letters above the previous. This consistent two-letter pattern makes memorising the key conversions straightforward for the women's (US 5 to US 8) and men's (US 8 to US 12) size ranges.
After converting your US size to UK and placing the order, confirm the UK retailer's free resize policy before completing payment. Most major UK jewellers — Goldsmiths, H.Samuel, Beaverbrooks, and Ernest Jones — offer a free first resize within 30–90 days of purchase. This policy converts any reasonable US-to-UK conversion estimate into a guaranteed correct fit. Note that some ring styles — full eternity rings, rings with stones set all the way around the band, and intricate base settings — cannot be resized. Confirm the specific ring's resizability with the retailer if there is any size uncertainty greater than half a UK letter.
The single most useful fact for quick US-to-UK mental conversion is the two-letter pattern: each whole US size number equals a UK letter that is two alphabet positions above the previous whole US number. US 5 = UK J½, US 6 = UK M, US 7 = UK O, US 8 = UK Q, US 9 = UK S, US 10 = UK U, US 11 = UK W, US 12 = UK Y. US half-sizes land exactly on the UK letters between these whole-number anchors: US 5½ = UK L, US 6½ = UK N, US 7½ = UK P, US 8½ = UK R, US 9½ = UK T, US 10½ = UK V. This two-letter pattern is accurate to within half a UK size across the entire range from US 4 to US 12 and is precise for all key anchor points. Always verify against the chart for sizes below US 5 or above US 12 where the pattern can drift by one UK half-size at the extremes.
When ordering from a UK jeweller's website with a US size, do not enter your US number directly into the UK size field — most UK websites only accept UK letters (A, B, C...N, O...) and will not recognise a US number. Convert your US size to a UK letter using the chart or calculator above, then enter the UK letter. If the UK website asks you to call or email for size confirmation before ordering, always do so — a 30-second confirmation call avoids the cost and delay of a return. When ordering a ring as a gift using a converted US size, always add a note to the order referencing your conversion (e.g., "Ordered as UK N converted from US 6½") so that if a resize is needed, the starting point is documented for the jeweller.
Canada uses the same ring size system as the United States — Canadian ring sizes are US ring sizes. If a Canadian retailer lists a ring as size 6½, this is identical to US 6½ = UK N. This is important because many UK buyers purchase online from Canadian retailers, and vice versa. No separate Canadian-to-UK conversion exists — use the US-to-UK chart and calculator on this page for all Canadian ring size conversions. The same applies to Mexican ring sizes, which also follow the US number scale. If a retailer describes itself as "North American sizing", it uses US numbers and this chart applies directly.
When converting in the reverse direction — UK letter to US number — use the same chart and calculator above (select "UK → US" in the converter). The reverse pattern is: UK M = US 6, UK N = US 6½, UK O = US 7, UK P = US 7½, UK Q = US 8, UK R = US 8½, UK S = US 9. If a US retailer asks for your ring size in US numbers and you know your UK letter, enter the US equivalent directly from this list or from the calculator. Note that the US system uses decimal notation (6.5 rather than 6½ on many online forms) — when entering US 6½ on a digital form, type 6.5, not 6½.
Wide-band rings — typically 6mm or wider — fit tighter than narrow bands at the same nominal US size. US jewellers standardly advise adding half a US size for wide-band rings before ordering. When you then convert this adjusted US size to UK, you get a UK size that already accounts for the wide-band effect. For example, if your standard US size is US 6½ (= UK N) but you are ordering a 6mm wide wedding band, your adjusted US size is US 7 (= UK O). Order UK O rather than UK N for the wide-band ring. This adjusted conversion gives the correct UK size for the wide-band style without any additional UK-side adjustment. Confirm this approach with the specific retailer, as wide-band sizing policies can vary between US and UK jewellers.