Determining Ring Blank Lengths in B. & S. Gauge  
      Metal Thickness, B.&S. Gauge  
  Sizes Length  
  (U.S.A.) (mm) 12 14 16 18 20 22 24  
  1 39.0 45.5 44.2 43.0 42.1 41.5 40.9 40.5  
  1 1/4 39.6 46.2 44.6 43.6 42.7 42.1 41.5 41.1  
  1 1/2 40.2 46.9 45.2 44.3 43.3 42.7 42.1 41.8  
  1 3/4 40.8 47.7 45.8 44.9 44.0 43.3 42.7 42.4  
  2 41.5 48.0 46.5 45.5 44.6 44.0 43.3 43.0  
  2 1/4 42.1 48.7 47.1 46.2 45.2 44.6 44.0 43.6  
  2 1/2 42.7 49.3 47.7 46.8 45.8 45.2 44.6 44.3  
  2 3/4 43.4 49.9 48.4 47.4 46.5 45.8 45.2 44.9  
  3 44.0 50.6 49.0 48.0 47.1 46.5 45.8 45.6  
  3 1/4 44.6 51.2 49.6 48.7 47.7 47.1 46.5 46.2  
  3 1/2 45.2 51.8 50.2 49.3 48.4 47.7 47.1 46.8  
  3 3/4 45.9 52.4 50.9 49.9 49.0 48.4 47.7 47.4  
  4 46.5 53.1 51.5 50.6 49.6 49.0 48.3 48.0  
  4 1/4 47.1 53.7 52.1 51.2 50.2 49.6 49.0 48.7  
  4 1/2 47.8 54.3 52.8 51.8 50.9 50.2 49.6 49.3  
  4 3/4 48.4 55.0 53.4 52.4 51.5 50.9 50.2 49.9  
  5 49.0 55.6 54.0 53.1 52.1 51.5 50.9 50.6  
  5 1/4 49.6 56.2 54.6 53.7 52.8 52.1 51.5 51.2  
  5 1/2 50.3 S6.8 55.3 54.3 53.4 52.7 52.1 51.8  
  5 3/4 50.9 57.5 55.9 55.0 54.0 53.4 52.8 52.4  
  6 51.5 58.1 56.5 55.6 54.6 54.0 53.4 53.1  
  6 1/4 52.2 58.7 57.1 56.2 55.3 54.6 54.0 53.7  
  6 1/2 52.8 59.3 57.8 56.8 55.9 55.3 54.6 54.3  
  6 3/4 53.4 60.0 58.4 57.5 56.5 55.9 55.3 55.0  
  7 54.0 60.6 59.0 58.1 57.1 56.5 55.9 55.6  
  7 1/4 54.7 61.2 59.7 58.7 57.8 57.1 56.5 56.2  
  7 1/2 55.3 61.9 60.3 59.3 58.4 57.8 57.1 56.8  
  7 3/4 55.9 62.5 60.9 60.0 59.0 58.4 57.8 57.5  
  8 56.6 63.1 61.5 60.6 59.7 59.0 58.4 58.1  
  8 1/4 57.2 63.7 62.2 61.2 60.3 59.7 59.0 58.7  
  8 1/2 57.8 64.4 62.8 61.9 60.9 60.3 59.7 59.3  
  8 3/4 58.4 65.0 63.4 62.5 61.5 60.9 60.3 60.0  
  9 59.1 65.6 64.1 63.1 62.2 61.5 60.9 60.6  
  9 1/4 59.7 66.3 64.7 63.7 62.8 62.2 61.5 61.2  
  9 1/2 60.3 66.9 65.3 64.4 63.4 62.8 62.2 61.9  
  9 3/4 60.9 67.5 65.9 65.0 64.1 63.4 62.8 62.5  
  10 61.6 68.1 66.6 65.6 64.7 64.1 63.4 63.1  
  10 1/4 62.2 68.8 67.2 66.3 65.3 64.7 64.1 63.7  
  10 1/2 62.8 69.4 67.8 66.9 65.9 65.3 64.7 64.4  
  10 3/4 63.5 70.0 68.5 67.5 66.6 65.9 65.3 65.0  
  11 64.1 70.7 69.1 68.1 67.2 66.6 65.9 65.6  
  11 1/4 64.7 71.3 69.7 68.8 67.8 67.2 66.6 66.3  
  11 1/2 65.3 71.9 70.3 69.4 68.5 67.8 67.2 66.9  
  11 3/4 66.0 72.5 71.0 70.0 69.1 68.5 67.8 67.5  
  12 66.6 73.2 71.6 70.7 69.7 69.1 68.5 68.1  
  12 1/4 67.2 73.8 72.2 71.3 70.3 69.7 69.1 68.8  
  12 1/2 67.9 74.4 72.8 71.9 71.0 70.3 69.7 69.4  
  12 3/4 68.5 75.0 73.5 72.5 71.6 7.0 70.3 70.0  
  13 69.1 75.7 74.1 73.2 72.2 71.6 71.0 70.7  
  Add 0.5mm to these lengths if the ring band is wider than 4mm.