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.
Brand fit: Ceramic and titanium at US 9 cannot be sized after firing, so the 18.9mm bore behind 59.5mm needs an exact measurement rather than a rounded guess.
US to ISO conversion
US to ISO is not a fixed jump, since US counts in fractions of an inch and ISO in whole millimetres of inner circumference: the gap climbs from 41 at US 3 to 58 at US 14. US 7 is ISO 54 and US 10 is ISO 62, and every US half size adds roughly 1.3 mm around the finger. Because ISO is a direct measurement, it is the value a jeweller sizes to, so converting from US to ISO turns an abstract number into millimetres you can check against a mandrel.
At this size, US to ISO
One size up from US 9, ISO moves 1 to ISO 61 while US rises 0.5 to US 9.5, so the two scales spread wider. Both US 9 and ISO 60 are whole numbers here, so nothing rounds. For US 9, the ISO column here runs ISO 58, ISO 60, ISO 61, stepping a full number at a time.
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 ISO? 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.
ℹ️
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.