I love knitting baby sweaters - they're so quick! The seamless raglan is my all time favorite construction, too. Plug in any yarn and color combo into this generic pattern formula, for dk, worsted, or aran weight yarn.
In this sweater, I worked 2 row color stripes, but use whatever stripe pattern suits you (great stashbusting opportunity here!) or go solid. When working stripes of 2 or more rounds, hide the color-change "jog" by knitting the entire round with the new color, then slip the 1st st of the second round. I made the cuffs, hem, and collar in K2-P2 ribbing, but you can just as easily work another rib, seed, garter, etc pattern, or just flow with the stockingnette roll.
You'll need a circular needle shorter than your sweater's chest circumference (I prefer 16" or 19"), a set of DPN's of the same size for the sleeves (or knit both at the same time on 2 circs or via the magic loop), and the same needles in a size or two smaller for the cuffs/hem, 4 stitch markers, 1 of which is unique to mark end-of-round (EOR), another marker for the sleeves, about 1 yard of smooth waste yarn, and a yarn needle to slips sts onto waste yarn as well as darn the ends.
Measure: Around chest, hip to underarm length, wrist to underarm length, around upper arm, around wrist, and around head (if he's not available, use measurements below). Now knit your gauge swatch with the larger needles, and calculate sts/inch (or sts/cm).
I like the work the sleeves first, so if my gauge is off or I don't like the yarn, I haven't wasted as much time as I would working the body. But if you want to work the body first, skip ahead.
Sleeves: On DPNs, CO enough sts equal to wrist size, plus a few extra for comfort, rounded up to a multiple of 4 if working 2x2 ribbing. Place marker and join to knit circularly, working a ribbed cuff for 1" (2.5cm). After ribbing, increase 2 sts every 8 rows at each side of marker (k1, inc, work to 1 st before end, inc, k1) until sleeve circumference reaches about 3" (7.5cm) more than than the upper arm size. Then knit even, if necessary, until sleeve is an inch or two longer than wrist to underarm length (babies grow fast), stop at marker, break yarn with a 12" (30cm) tail. Make a 2nd sleeve exactly like the 1st.
Tip: If using DPN's, leave the 1st sleeve on the larger needles, start the 2nd sleeve with the smaller ones for the cuff, then when ready for the larger ones, trade needles.
Body: add 4" (10 cm) to the chest size, then multiply that sum by the sts/inch (gauge), round up to a multiple of 4 for 2x2 ribbing, and CO that number of sts onto your smaller circular, place EOR marker, and join to knit circularly. Work ribbed hem for about 1" (2.5cm). Don't forget to change to the larger needles after the hem! Work even until your tube measures hip to underarm length. Work 1 more round, placing 2nd marker at the halfway point in the round, continue on, but stop knitting at 1.5" of sts (4cm) before the EOR marker, then slip those last sts onto a piece of waste yarn.
Yoke: On both sleeves, slip the first 1.5" of sts (4cm), the exact same number as you did on the body, onto waste yarn. (These underarm sts you'll sew/graft together later). Holding the body needle in your right hand, place EOR marker onto that needle, and using the yarn from the body, knit the remaining sleeve sts off the DPN's onto the body needle, place 2nd marker, knit across body sts to 1.5" of sts (4cm) before halfway marker, and slip those few sts onto waste yarn. Slip your marker to the right needle, work the 2nd sleeve sts, then place the last marker, and finally work to EOR.
Now you'll continue in the round, on the one circular needle. Starting with your EOR marker, then M2, M3, M4, the sts are divided as follows: right shoulder, back, left shoulder, and front.
Work even for an 1.5" worth (4cm) of rounds. Now you're ready for raglan decreases.Rnd 1: Beginning at EOR marker, k1, k2tog, work to 3 sts before M2, ssk, k2, k2tog, work to 3 sts before M3, ssk, k2, k2tog, work to 3 sts before M4, ssk, k2, k2tog, work to 3 sts before EOR, ssk, k1.
Rnd 2: Work even.
Neck: Repeat last 2 rounds until neck opening measures head circumference. Now use short rows to knit back & forth to raise the back of the neck. For this explanation, knit means working with the front side facing, and purl means working with the wrong side. Obviously, if you're using another stitch pattern, you'll need to compensate.
Knit the round, making dec's as usual, but after making the dec before M4, stop 1 st before that marker, wrap & turn, purl even back to 1 st before EOR, w&t, knit even to halfway between M3 and M4 while making dec's at M2 & M3, w&t, purl even to halfway between M2 & EOR, w&t, knit even to 3 sts past M3, w&t, purl even 3 sts past M2, w&t, knit even to 3 sts before M3, w&t, purl even to 3 sts before M2, w&t, then knit even to EOR.
Now continue in the round again, working a neck ribbing for about an inch. Bind off LOOSELY, using a sewn BO. DO NOT use the standard pullover BO - it has very little stretch, and if you do it on big enough needles enough to fit over the head, you get a loose, sloppy edge.
Half-hitch BO: Cut yarn leaving 4 times the length of your BO edge, thread on needle, insert needle thru 2nd st as if to knit, passing needle to back of work, tighten gently, insert needle thru 1st st as if to purl, passing needle to front of work, and drop 1st st off needle. Repeat till 1 st remains, then insert needle as if to knit, passing needle under the BO strand between this last st and the one before, and tighten. To hide the BO jog, insert needle under both the 1st BO strand and the first BO sts, pull snug, then weave end your end.
Now all you have left are two small underarm "seams" to sew, graft, or 3-needle bind off. Weave in ends, wash sweater, put it on the baby, and take cute photos.
If you want to use my schematics for a roomy 6 to 18 month old sweater, just make the actual measurements 22" around the chest, 8" long in both the body and sleeves to the underarms, 5" around the cuff to 8" around upper arm, and work the neck to 18" before continuing with short-rows. This will be a big sweater for young babies, but it will grow nicely with them, as sleeves can roll for now, and babies don't care if the ribbed hem falls at the widest point of their hips.
Latest correction/update added Jan. 22, 2008.
Latest correction/update added Jul. 29, 2008.