How do I know how to calculate a cap & neck size?
 Article Title: How do I know how to calculate a cap & neck size?Article Summary: A brief explanation on understanding the cap & neck finish on bottles. Article Date: 7/21/2003Article ID: 625 Share This:

Cap and Neck Finishes
Screw thread cap sizes are generally expressed as two numbers. The first number refers to the cap diameter (in millimeters) and the corresponding Glass Packaging Institute (GPI)/Society of the Plastics Industry (SPI) finish diameter. The second number refers to the height and thread configuration of the closure or finish. The following is a selection of commonly used caps and finishes:
Neck Finish Dimensions
"I" Dimension
The inner diameter of the bottle neck. Specifications require a minimum "I" to allow sufficient clearance for filling tubes. Liner-less closures, with a plug or land seal, and dispensing plugs and fitments require a controlled "I" dimension for a proper fit.
"T" Dimension
The outside diameter of the thread. The tolerance range of the "T" dimension will determine the fit between bottle and closure.
"E" Dimension
The outside diameter of the neck. The difference between the "E" and "T" dimensions, divided by two, determines the thread depth.
"H" Dimension
The height of the neck finish. Measured from the top of the neck to the point where the diameter "T", extended down, intersects the shoulder.

"S" Dimension
Measured from the top of the finish to the top edge of the first thread. The "S" dimension is the key factor which determines the orientation of the closure to the bottle and the amount of thread engagement between the bottle and cap.

 MM T min  max E min  max 400H min  max 410H min  max 415H min  max S min  max I 13 .514  .502 .454  .442 -          - -        - .457  .437 .052   .022 .218 15 .581   .569 .521   .509 -          - -        - .572  .542 .052   .022 .258 18 .704   .688 .620   .604 .385   .355 .536 .508 .632  .602 .052   .022 .325 20 .783   .767 .699   .683 .386   .356 .569 .539 .757  .727 .052   .022 .404 22 .862   .846 .778   .762 .386   .356 .600 .570 .852  .822 .052   .022 .483 24 .940   .924 .856   .840 .415   .385 .661  631 .972  .942 .061   .031 .516 28 1.088 1.058 .994   .974 .415   .385 .723   .693 1.097  1.067 .061   .031 .614 30 1.127 1.107 1.033 1.013 .418   .388 -        - -        - .061   .031 .653 33 1.265 1.241 1.171 1.147 .418   .388 -        - 1.289 1.259 .061   .031 .791 35 1.364 1.340 1.270 1.246 .418   .388 -        - -        - .061   .031 .875 38 1.476 1.452 1.382 1.358 .418   .388 -        - -          - .061   .031 .987 40 1.580 1.550 1.486 1.456 .418   .388 -          - -          - 061   .031 1.091 43 1.654 1.624 1.560 1.530 .418   .388 -        - -          - .061   .031 1.165 45 1.740 1.710 1.646 1.616 .418   .388 -        - -          - .061   .031 1.251 48 1.870 1.840 1.776 1.746 .418   .388 -        - -        - .061   .031 1.381 51 1.968 1.933 1.874 1.839 .423   .393 -        - -          - .061   .031 1.479 53 2.067 2.032 1.973 1.938 .423   .393 -        - -          - .061   .031 1.578 58 2.224 2.189 2.130 2.095 .423   .393 -        - -          - .061   .031 1.735 60 2.342 2.307 2.246 2.213 .423   .393 -        - -          - .061   .031 1.883 63 2.461 2.426 2.367 2.332 .423   .393 -        - -          - .061   .031 1.972 65 2.579 2.544 2.485 2.450 .423   .393 -          - -          - 061   .031 2.090 70 2.736 2.701 2.642 2.607 .423   .393 -        - -          - .061   .031 2.247 75 2.913 2.878 2.819 2.784 .423   .393 -          - -          - 061   .031 2.424 77 3.035 3.000 2.941 2.906 .502   .472 -        - -          - .075   .045 2.546 83 3.268 3.233 3.148 3.113 .502   .472 -        - -          - .075   .045 2.753 89 3.511 3.476 3.391 3.356 .550   .520 -        - -          - 075   .045 2.915 100 3.397 3.902 3.817 3.782 .612   .582 -        - -          - 075   .045 3.344 110 4.331 4.296 4.211 4.176 .612   .582 -        - -          - 075   .045 3.737 120 4.724 4.689 4.604 4.569 .700   .670 -        - -          - 075   .045 4.131

 MM 13 15 18 20 22 24 28 30 33 35 38 40 43 45 48 Thread/Inch 12 12 8 8 8 8 6 6 6 6 6 6 6 6 6

 MM 51 53 58 60 63 65 70 75 77 83 89 100 110 120 Thread/Inch 6 6 6 6 6 6 6 6 6 5 5 5 5 5