Simple pattern -- I love the classic look of this sweater…it looks great on both my boys!

I’d definitely do the hard work of measuring the kid, calculating stitches/inch and figure out your size from there. The # of stitches I cast on for my 10-year old’s sweater was listed as a 4-6 yr old (granted, my yarn was slightly bigger…but not by that much!). I figured out sleeve and torso length by measuring it against another one of his shirts.