Zipper Length Question

Hi everyone,  I need to ask what may be a silly zipper question.  When making something with a zipper closure, like a purse or a pouch, how do you decide what size zipper you should buy?  I know you can trim a zipper if it's too long, but if you're going to buy one specifically, how do you decide what size?  Should the entire length of the zipper be the same length as your fabric, or do you line up where the zipper starts and ends with the edges of your fabric?  Thanks for your help!

I like to use a zipper that's a bit shorter than the width of my bag and add little fabric tabs to the ends.  I find that if I am sewing the bag together with the zipper going all the way to the sides of the bags, it makes for a very chunky seam that is hard to turn properly.  I hope this makes sense!  I think you can see what I mean in this post:
http://kleiosbelly.wordpress.com/2009/04/18/yellow-diversions/

best, mara

It also depends on how you are putting your zipper in. If you are stitching it directly on the bag or in a gusset. You can make a zipper thats too short longer with fabric ends or cut down one thats too long. I usually start with a zipper that is close in size to my purse front & back.

I'm still a little confused...this is what I meant by the size of the zipper, in comparison to the fabric pieces.  Which one is right?  Should the whole zipper be the same length of the fabric, or just where it starts and stops?



Also, I like the idea of the tabs, that sounds like a good way to make it look more polished.  I will definitely try that.

Are you doing an exposed insertion or a lapped insertion? I think it's easier to make a cleaner insertion either way if the entire zipper tape is the same length or shorter than the length of the fabric. Like the one on the left. That way you only end up with zipper tape in the seam and not the bulky coil.

I agree with random-charm. If you have the ends in the seam & not the coil it will be much easier to sew & not pucker up.

I agree with the others.  In order to keep the bulk out of the seams, the zipper should be a tad bit shorter than the length of the fabric.  And I highly recommend the tabs.  It will give the whole area a neat and finished look.

Thanks everybody, that answers my question!  I did it the way on the right the first time, so that must be why it puckered badly.  I had just chalked it up to not knowing how to do it right. 

Random-Charm:

I obviously have some more reading and learning to do on zippers because I don't have a clue what exposed insertion and lapped insertion mean!