Sizing problem

I’m knitting a jacket/sweater for my 13-month-old grandson–it’s a rectangle back, then 2 fronts, then 2 sleeves. I’m using the size 18-24 mo. size, but my rectangle back if exactly 1" narrower than it’s supposed to be. I know I’m a tight knitter, but I swear I swatched it–actually I thought it might be a little big. I really wanted him to be able to wear it at least 1-1/2 years, but his t-shirts are 12" wide right now (it’s also the actual width of the rectangle I’m currently knitting which is supposed to be 13" for the 12-18 month size). I’m going to have to start over aren’t I? And I suppose use the size 3 pattern?

Please remember that using the size 3 pattern will not give me the correct width of a size 3 jacket–it will only give me the correct width for the 18-24 month size so then will everything else be out of whack?

Use larger needles, especially if you knit tight. That should give you an extra inch or so. Or if there’s larger than the 18-24mo size, go for that.

I’m using size 9 on worsted weight Berrocco–I’m afraid 10’s will make it look too “holey”. Would you try the 10’s or just go up to the next size jacket. It seems weird to be knitting a size 3 for a 13-month-old cause he’s not a really big baby, but whatever…

If you knit tight the 3 yo size won’t be that big. Take your sts/inch and see how many inches the larger size will end up at your gauge. Divide the front/back sts by your gauge. If it’s about what the 18-24 mo size is, then use it, but do the length measurements somewhere between the 24mo and size 3.

Sorry to be dumb, but you lost me here on the width part.
If the length measurement is 15 for 18-24 months, and 16 for 3 year old old, use 15-1/2 length?

My pattern is on Lions Heart “Patrick’s 1st Jacket” and I can’t tell how much yarn I’ll need for 3 year old size. Can you look at it for me please. Sorry to be so dumb…

Since there’s only about an inch difference in length, then go ahead with the longer measurement.

Lion and Red heart are two different sites. It’s a Lion pattern though. You’ll need the amount given for the size 3, which is 800 yds of one color and 600 of the other. If you’re going to make it all one color though, you probably need less altogether.

That seems like a lot of yarn, though, it would be over 1200 yds for a child’s size 3 jacket? It does take more yarn for garter stitch, and if you use more colors, but for a single color I would expect it to only take about 600-800 yds at most.

I don’t understand what you’re saying here.

Divide your sts per inch into the total number of front and back sts at the chest for size 3 and see what that comes out to.