Please note any zipper should be fully zipped up before the measurement, regardless of its type.

Open Ended Zipper
For a standard open ended zipper, the length is measured from the top end of the Zipper Slider to the tip of the Open Part, exclusive of the Forth Head Tape. You will end up with a shorter zipper if you mistakenly include the Forth Head Tape.

Close Ended Zipper
For a standard close ended zipper, the length is measured from the top end of the Zipper Slider to the tip of the Bottom Stop, exclusive of both the Forth Head Tape and Back Head Tape. You will be left with a shorter zipper if you mistakenly include either the Forth Head Tape or Back Head Tape.

Two Way Open Ended Zipper
For a standard two way open ended zipper, the length is measured from the top end of the Zipper Slider to the bottom end of the Reinforce Tape to the tip of the Open Part, exclusive of the Forth Head Tape.

Two Way Close Ended Zipper      
Two way close ended zipper further falls into O shape and X shape. Both types include double zipper sliders.  The main difference lies in that the former contains 2 bottom stops with the sliders installed in head-to-head relation, while the latter includes 2 top stops with the sliders installed in bottom-to-bottom relation.

For a standard two way close ended zipper in O shape, the length is measured from the tip of one Bottom Stop to that of the other Bottom Stop, exclusive of both the Forth Head Tape and Back Head Tape.

For a standard two way close ended zipper in X shape, the length is measured from the top end of one Zipper Slider to that of the other Zipper Slider, exclusive of both the Forth Head Tape and Back Head Tape.