Uk ring sizer compared with international measurements with indication of diameter and circumference. If you know the diameter of a ring you can easily get the conventional ring size by looking at the table below. Remember that the ring size is not the measure of the diameter or even the circumference. If you need to take the ring size on a finger it is not appropriate to take the circumference with the classic tape measure because applying more or less pressure make the measurements not accurate. Instead, you would measure an existing and comfortable ring using a calliper (either digital or mechanical) making sure to take more than one measurement as used rings never have a perfectly circular stem.


Remember that between two consecutive measurements the difference is only one millimetre in the circumference, that's why you need to be very precise
Otherwise you can print our PDF ring to determine the ring sizes by direct comparison with virtually no error margin, if used correctly.
One factor to consider when we want to measure the size of a ring is that the fingers do not always have the same diameter but they swell up a bit in the summer while they shrink a bit in winter.

 

UKItalian/SwissDiameter mm.USA/CanadaFrenchJapaneseGermanCircumference mm.
F414.034441444.0
 514.3 45  45.0
G14.33 ½ 514 ½45.2
H614.6 46  46.0
H ½14.84 71546.5
I715.0 47  47.0
815.34 ½488 48.0
J915.6 49 15 ¾49.0
K1015.9 50  50.0
L 16.15 ½   50.3
1116.2 5111 51.0
  16.46 1216 ½51.5
M 16.5    51.8
 1216.6 52  52.0
N1316.953  53.0
  17.1    53.4
O1417.27541417 ¼54.0
 1517.5   17 ½55.0
P1617.87 ¾   56.0
Q1718.1857161857.0
R1818.58 ½581718 ½58.0
 1918.8    59.0
S2019.1959181960.0
T2119.4   19 ¾61.0
 2219.71062  62.0
U 19.9  21 62.5
2320.010 ½ 2220 ½63.0
V 20.3 64  63.8
2420.411 2320 ¾64.0
W2520.7 65  65.0
X2621.0 66  66.0
 2721.31266 ½25 67.0
Y 21.512 ¼67 21 ½67.5
 2821.712 ½67¾2621 ¾68.0
Z 21.9 68  68.8
 2922.0    69.0
Z+13022.31370272270.1