How do I know how to calculate a cap & neck size?

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

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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:
7/21/2003
Article ID:
625
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