I am knitting a baby sweater and the pattern says "to make a 3-6 month size, start the same way, making the back about an inch wider. Sleeves will automatically be wider." So, should I do more raglan increases and then do I just measure across the back? What should the back measurement be then for a 3-6 month size? The pattern I am using is the No Seam Raglan Baby Sweater by Carole Barenys.
I am making the exact same sweater right now in the 3-6 month size. I know she says to make the back about an inch wider, but she doesn't say that you will need to increase the total stitches on the fronts by the same amount. Her given gauge is 6 stitches to the inch, so that means you add 6 stitches to the back and 3 stitches to each of the fronts.
I haven't altered the sleeve width, but I have incorporated the "seam" stitches to the sleeves at the underarm.
If you keep to the raglan increases she gives and divide for the body and sleeves when your work measures 5 to 5 1/2 inches, it should be fine. If in doubt, make this section a few rows longer. Nothing worse than a garment that's too tight under the arms.
This is about the fourth garment I have knitted to this pattern and they all fit beautifully.