No, your gauge is going to be too big to use 120 sts. at 4½ sts/inch (if that is what you get, nevermind what the yarn label says) that would be 26½", far too large, you want a hat [I]smaller[/I] than the actual head size because of the stretch. 100 sts will give you 22" which should be about right for a head that measure 23-25". However, you first have to find out how many sts/inch you get. It might be 4¼ or 4 3/4.
Ok, so the 100 sts cast on should be okay for the woman’s head and the man’s head. I guess if I think about it, many hats that are knits tend to be “one size fits all” which is possible because of the stretch.
Thank you again for all your help! I will definately keep you updated as I go along!
I have cast on 100 stitches, and have about 2-3 inches done so far. The only thing is that just resting on the needles (I’m using circular), it measures 15" around. That is the hat “relaxed”, meaning not stretched. The thing is it just doesn’t look like it could stretch to fit a 25" head. It doesn’t look possible for the hat to stretch a full 10 inches. Maybe I should redo it and cast on 120 stitches?
Hmmm. . .I don’t know. . .It’s been a few months since I made (and gave away) the 2 I did, so I can’t remember exactly what the measurement was, laying flat. But I’m looking at a ruler, and 7.5" looks about right-- is that what you get if you lay it flat, about 7.5" across? It is very stretchy, meant to fit quite close. Are you on Ravelry? If so, look it up there and look at the photos. If not, if you just google “jacques cousteau hat” in images, you should be able to see some examples. For example, the hat is very pointy at the top when off of a head, but on, it smooths out to a spiral. I mean-- it really is supposed to be a very close fit. Oh-- and was your test swatch coming out to 4.5"? If so, then I would just keep going the way you are.
Measure it both relaxed and stretched out. It should be about an inch or 2 less than the head measurement.
Ooooo, I wouldn’t do just an inch or 2 smaller relaxed for this one. Look at the photos on the directions page: http://typyp.ajatukseni.net/2008/11/12/jacques-cousteau-hat/
There’s a photo of a red one on someone’s head, and then if you scroll down, there’s one just sitting there-- the ribs are much more compact when not on the model’s head. This one is supposed to really stretch out when on.
Well, I undid it to redo it to cast on 120 stitches 
If it was 15 inches around, then yeah that would put it at 7.5 diameter across, relaxed. It just seems like an awful long way for it to stretch to make it to 25 inches.
I am not a member of ravelry, so I’ll just look at pictures. I’m just not sure if the 120 stitches would be too big? I guess since the hat is made to stretch, it just wouldn’t need to stretch as far as the 100 stitches one?
One other thing, for this hat (which is somewhat similar) the cast on is 100 stitches, so maybe it would be okay.
Oh-- I thought you were making the smaller (22") size? But if you want the bigger (25.5") one, then definitely, I’d go with the 120 sts.
yeah I cast on the 120 stitches, so we’ll see how that goes! I guess it would just not need to stretch so much over the head.
I am at the decreasing stage! It does seem the 120 stitches did the trick, it is looking really good, thank you again for the help! 
Yay!:cheering:
Yay just finished it! It turned out really well! So the 120 stitch cast on is good! :mrgreen: I’ll have to get some pictures!
Here is the hat, it is black even though the flash makes it look charcoal.
The top swirl
Side view
Brim folded up
Brim folded down
It came out perfectly! So what was the final measurement across, when laid flat, near the bottom?
That came out great!
The measurement across the bottom laid flat is 7.5 inches, so that would be a circumference of 15 inches, and that is the hat laying “relaxed”.