US 9 falls in the men's range near 60 mm; Russia and the CIS would call the same ring by its diameter, about 19 mm, since their scale counts millimetres across rather than around.
US to UK conversion
US ring sizes are numbers while UK uses letters, and they climb together at half a US size per letter: US 6 is UK L, US 7 is UK N, US 8.5 is UK Q. Each half step up the US scale moves one letter along the UK alphabet, so US 6.5 sits at UK M. Because a single letter covers a half US size, a UK letter is a coarser label, and a ring right at the join of two letters is where cross-shop conversions most often slip.
At this size, US to UK
One size up from US 9, UK steps to UK S while US rises 0.5 to US 9.5. This size runs a 18.9 mm bore.
Ring Sizes Around US 9 US UK ISO / EU JP / KR Diameter (mm) Circumference (mm) 7.5 O 56 15 17.7 55.7 8 P 57 16 18.1 57 8.5 Q 58 18 18.6 58.3 9 R 60 19 18.9 59.5 9.5 S 61 20 19.4 60.8 10 T 62 21 19.8 62.1 10.5 U 63 23 20.2 63.4
Frequently Asked Questions Does US 9 round up or down in UK? For a broad men's band at 9, round up about a half size: a wide ring binds where a narrow one clears, and resizing a finished band is harder above this width.
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Note ISO 8653:2016 sets the size as inner circumference in mm; France and Germany label by the same number, so a ring bought anywhere in Continental Europe needs no conversion. Japan and Korea share one scale: 1 gou is a 13.0 mm bore and each step adds a third of a millimetre, so US 7 (17.3 mm) is 14 gou and 14 ho. Russia and the CIS size by inner diameter in mm to the nearest 0.5, so US 7 is a 17.5 there. A band wider than 6 mm is usually sized up about half a size, and a finger can swing close to a full size between a cold morning and a hot afternoon, so measure warm and late in the day. See a number that looks off? Report an error on this page.