Picking up Stitches around a Neck Edge of a Sweater

What if you make a sweater that has a loose crew neck, but once you you've sewed in up you think it would be better with a turtle neck, question is:

How to you figure out how many stitches to pick up around the necks edge?

YOUR ANSWER

If this was my sweater, I would probably knit the turtle neck using the same number of stitches as you would for the crew neck, but use smaller needles and knit the neck in rib. If you have rib at the bottom of your sweater, you would knit on the needles you used for that rib and knit the same type of rib (i.e., 1 x 1, or 2 x 2) so that it matches.

Rib is quite elastic so the turtle neck should stretch wide enough to go over your head but sit snuggly against your neck when you are wearing it. If you want to you can knit the first half of the rib on the smaller needles and then change to larger needles (only go up one or two sizes) so that the part of the neck that is folded down is slightly looser.

When you cast off you will need to cast off as loosely as possible to make sure that the cast off edge is wide enough to go over your head.