It's really a very personal thing but the goal for any sweater ought to be a length that makes you feel good. I know that in my sweater chest, length has varied dramatically and will probably continue to vary dramatically sweater by sweater. It depends how I am planning on wearing the sweater.
My first sweaters tended to be shorter. I measured this one today,
I loved this sweater then. It is 11.5 inches long and it was my favourite sweater to wear when I was still doing office work. It was warm with its heavy collar at my neck and the short sleeves never let it be too warm. It is quite perfectly me and I still wear this sweater regularly. It was perfect then, but I do wish it was a little longer now, another two inches. I didn't want a sweater that dragged under a chair seat back then and I didn't want it to get caught in the chair wheels if it was on the back of my chair but now, they can drag all they want.
This one, the sweater I wear more than any other, because it is great alone and perfectly wonderfully spacious to wear a vest or another sweater under. Just my favourite relaxed garment ever.
It is 15 inches from the underarm and is really quite perfectly me. The only change I would make is to make the bottom curved hem into short rows. This way of making that curved edge, causes it to roll under a bit rather than laying nice and flat. I am going to make another of these soon.
And then this one,
Which is 18 inches and is much more a tunic than a sweater. I love wearing this sweater and it is again, very perfectly me. The only thing I would change is that I would make the neckline smaller. It is a very wide neckline, to the point of falling off my shoulders wide. I did a row of crochet around the neckline to stop it from doing so, but I need to do it again in a yarn with a bit less give to make it comfortably wearable again.
My last cardigan,
is 18 inches long too, which kind of explains why I think it is a little too long. It doesn't change when I wear it though.
And my little red sweater, knit for a very different purpose
is 16 inches. Which reminds me that I need to take a finished photo of this little topper.
Each of these sweaters filled a very different purpose in my wardrobe, the first, something to stop the air conditioner blowing on my neck at the office, the second, and every man, every day sort of sweater, the third, a tester sweater in several different ways, one of which was to see if I liked how longer sweater lengths felt wearing and if I like them on me. Then one, which was just a joy to knit and which strangely enough, was knit to what I thought was my optimal sweater length but that isn't how I feel when wearing it. Last, a little something to wear over top my plain wardrobe to make it a dressier and give what I wear a little pop of vibrant colour.
My comfortable length is probably between 15 and 18 inches, which is a pretty large variance. I do think it is going to continue being something that depends on what I am knitting the sweater for.
Hahahaha, I just went to measure yet another sweater, the one that unfailingly gets commented on, particularly for colour, which I have no finished photo of. 18.5 inches.
This has been fun!