Ring Size Conversions

 

Inside Diameter
(inches
)

Inside Diameter
(mm)

Inside Circumference
(inches)

Inside Circumference
(mm)

Number Sizes
US/Canada
Standard

Letter Sizes
British Irish Australian
NZ Equivalent

 
0.57014.51.79045.53 1/2G
0.57814.71.81546.13 3/4G 1/2
0.58614.91.84046.74
0.59415.11.86547.44 1/4H 1/2
0.60215.31.89048.04 1/2
0.61015.51.91548.74 3/4J
0.61815.71.94149.35J 1/2
0.62615.91.96649.95 1/4K
0.63416.11.99150.65 1/2K 1/2
0.64216.32.01651.25 3/4L
0.65016.52.04151.86L 1/2
0.65816.72.06652.56 1/4
0.66616.92.09153.16 1/2M 1/2
0.67417.12.11653.86 3/4N
0.68217.32.14154.47N 1/2
0.69017.52.16755.07 1/4
0.69817.72.19255.77 1/2O 1/2
0.70617.92.21756.37 3/4
0.71418.12.24256.98P 1/2
0.72218.32.26757.68 1/4
0.73018.52.29258.28 1/2Q 1/2
0.73818.72.31758.98 3/4R
0.74618.92.34259.59R 1/2
0.75419.22.36860.19 1/4S
0.76219.42.39360.89 1/2S 1/2
0.77019.62.41861.49 3/4T
0.77819.82.44362.110T 1/2
0.78620.02.46862.710 1/4U
0.79420.22.49363.310 1/2U 1/2
0.80220.42.51864.010 3/4V
0.81020.62.54364.611V 1/2
0.81820.82.56965.211 1/4W
0.82621.02.59465.911 1/2W 1/2
0.83421.22.61966.511 3/4X
0.84221.42.64467.212X 1/2
0.85021.62.66967.812 1/4
0.85821.82.69468.412 1/2Z
0.86622.02.71969.112 3/4Z 1/2
0.87422.22.74469.713 
0.88222.42.76970.313 1/4Z1
0.89022.62.79571.013 1/2 
0.89822.82.82071.613 3/4Z2
0.90623.02.84572.314Z3
0.91423.22.87072.914 1/4 
0.92223.42.89573.514 1/2Z4