Hand-crafted Knot Jewelry:
Decorative Marlingspike Seamanship rendered in precious metal.
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Sizes are approximate, use with caution. Ideally, have your finger size measured by a jeweller, and inform him that you are planning to get a very wide ring.
USA  Size Diam. -inch Diam. in mm Circ. -mm British  French  German  Japanese  Swiss 
0000 .390 9.91   -        
00 .422 10.72   -        
0 .454 11.53   -        
1/2 .474 11.95   A        
3/4 .482 12.18   A 1/2        
1 .487 12.37 38.9 B     1  
1 1/4 - 12.60 39.6 B 1/2        
1 1/2 .503 12.78 40.2 C        
1 3/4 - 13.00 40.8 C 1/2        
2 .520 13.21 41.5 D 41 1/2 13 1/2 2 1 1/2
2 1/4 - 13.41 42.1 D 1/2 - -    
2 1/2 .536 13.61 42.7 E 42 3/4 13 3/4 3 2 3/4
2 3/4 - 13.83 43.4 E 1/2 - -    
3 .553 14.05 44.0 F 44 14 4 4
3 1/8 - 14.15 44.3 F 1/2 - -    
3 1/4 - 14.25 44.6 - - -    
3 3/8 - 14.36 44.9 G 45 1/4 - 5 5 1/4
3 1/2 .569 14.45 45.2 - - 14 1/2    
3 5/8 - 14.56 45.6  G 1/2 -   6  
3 3/4 - 14.65 45.9 H 46 1/2     6 1/2
4 .585 14.86 46.5 H 1/2 - 15 7  
4 1/4 - 15.04 47.1 47 3/4     7 3/4
4 1/2 .601 15.27 47.8 I 1/2 - 15 1/4 8  
4 5/8 - 15.40 48.1 J 49 15 1/2   9
4 3/4 - 15.53 48.4 - -      
5 .618 15.70 49.0 J 1/2 - 15 3/4 9  
5 1/8 - 15.80 49.3 K 50     10
5 1/4 - 15.90 49.6 - -      
5 3/8 - 16.0 50.0 K 1/2 -   10  
5 1/2 .634 16.10 50.3 L 51 3/4 16   11 3/4
5 3/4 - 16.30 50.9 - -      
5 7/8 - 16.41 51.3 L 1/2 -      
6 .650 16.51 51.5 M 52 3/4 16 1/2 12 12 3/4
6 1/4 - 16.71 52.2 M 1/2 -      
6 1/2 .666 16.92 52.8 N 54 17 13 14
6 3/4 - 17.13 53.4 N 1/2 -      
7 .683 17.35 54.0 O 55 1/4 17 1/4 14 15 1/4
7 1/4 - 17.45 54.7 O 1/2 -      
7 1/2 .699 17.75 55.3 P 56 1/2 17 3/4 15 16 1/2
7 3/4 - 17.97 55.9 P 1/2 -      
8 .716 18.19 56.6 Q 57 3/4 18 16 17 3/4
8 1/4 - 18.35 57.2 Q 1/2 -      
8 1/2 .732 18.53 57.8 - - 18 1/2 17  
8 5/8 - 18.61 58.4 R 59     19
8 3/4 - 18.69 58.4 - -      
8 7/8 - 18.80 59.0 R 1/2 -      
9 .748 18.89 59.1 - - 19 18  
9 1/8 - 19.10 59.4 S 60 1/4     20 1/4
9 1/4 - 19.22 59.7 - -      
9 3/8 - 19.31 60.0 S 1/2 -      
9 1/2 .764 19.41 60.3 - - 19 1/2 19  
9 5/8 - 19.51 60.6 T 61 1/2     21 1/2
9 3/4 - 19.62 60.9 - -      
10 .781 19.84 61.6 T 1/2 - 20 20  
10 1/4 - 20.02 62.2 U 62 3/4   21 22 3/4
10 1/2 .797 20.20 62.8 U 1/2 - 20 1/4 22  
10 5/8 - 20.32 63.1 V 63     23 3/4
10 3/4 - 20.44 63.5 - -      
11 .814 20.68 64.1 V 1/2 - 20 3/4 23  
11 1/8 - 20.76 64.3 W 65     25
11 1/4 - 20.85 64.7 - -      
11 3/8 - 20.94 65.0 W 1/2 -      
11 1/2 - 21.08 65.3 - - 21 24  
11 5/8 .830 21.18 65.7 X 66 1/4     26 1/4
11 3/4 - 21.24 66.0 - -      
11 7/8 - 21.30 66.3 X 1/2 -      
12 .846 21.49 66.6 Y 67 1/2 21 1/4 25 27 1/2
12 1/2 .862 21.89 67.9 Z 68 3/4 21 3/4 26 28 3/4
12 3/4 - 22.10 68.5 Z 1/2 -      
13 .879 22.33 69.1 - - 22 27  


For myself, I've measured a few ring-sizers and derived the slope of the line, then plotted it on a chart, to get any fractional size. Here's a chart of quarter-sizes:

You may note that some of the sizes are not exactly the same as the above chart. Probably my fault, but I consider them within a reasonable margin of error.

Size Dia. Circ.
1.00 0.493 1.549
1.25 0.501 1.574
1.50 0.509 1.599
1.75 0.517 1.624
2.00 0.525 1.649
2.25 0.533 1.674
2.50 0.541 1.699
2.75 0.549 1.724
3.00 0.557 1.749
3.25 0.565 1.774
3.50 0.573 1.800
3.75 0.581 1.825
4.00 0.589 1.850
4.25 0.597 1.875
4.50 0.605 1.900
4.75 0.613 1.925
5.00 0.621 1.950
5.25 0.629 1.975
5.50 0.637 2.000
5.75 0.645 2.025
6.00 0.653 2.050
6.25 0.661 2.075
6.50 0.669 2.100
6.75 0.677 2.126
7.00 0.685 2.151
7.25 0.693 2.176
7.50 0.701 2.201
7.75 0.709 2.226
8.00 0.717 2.251
8.25 0.724 2.276
8.50 0.732 2.301
8.75 0.740 2.326
9.00 0.748 2.351
9.25 0.756 2.376
9.50 0.764 2.401
9.75 0.772 2.426
10.00 0.780 2.452
10.25 0.788 2.477
10.50 0.796 2.502
10.75 0.804 2.527
11.00 0.812 2.552
11.25 0.820 2.577
11.50 0.828 2.602
11.75 0.836 2.627
12.00 0.844 2.652
12.25 0.852 2.677
12.50 0.860 2.702
12.75 0.868 2.727
13.00 0.876 2.752
13.25 0.884 2.778
13.50 0.892 2.803
13.75 0.900 2.828
14.00 0.908 2.853
14.25 0.916 2.878
14.50 0.924 2.903
14.75 0.932 2.928
15.00 0.940 2.953
15.25 0.948 2.978
15.50 0.956 3.003
15.75 0.964 3.028
16.00 0.972 3.053
16.25 0.980 3.078

(This site last updated on 12-11-2017)

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