The top-down, raglan framework is based on percentages and proportion but since we are each uniquely shaped sometimes we have to add a couple stitches here and there to make a perfectly fitting sweater. There are a couple ways to add the extra stitches that you may need, increasing the raglan length, casting on the needed stitches under each arm or by using short rows to make some darts.
As you increase at the raglan seams you are adding stitches to both the body and the sleeves. So if you are a couple stitches short of your desired amount of stitches for the chest you can simply work one or two more increase rows. This method of increasing is great while you are increasing the neckline but if you want to add inches a larger number of stitches to your chest measurement but not your sleeves you will need to use another method.
A very simple way to add additional stitches is to cast on half of the stitches that you wish to add under each arm immediately after you have separated the sleeves from the body. You easily add up to 2 inches worth of stitches under each arm without really affecting how the sleeve and body of the sweater meet. It will create a small hole but since there is often a small hole that you’ll need to seam together anyway, you’re not really creating any extra work for yourself.
The third way you can add some room is to add some darts using short rows. Darts are often used in sewing to create a nicely shaped garment, in knitting they serve the same purpose. The type of darts I find best suited for use with this style of sweater is a vertical dart. Vertical darts use increases or decreases at the same spot in each row to change the size of the bust area. You are probably used to using increases and decreases to shape sleeves or raglan seam and in those areas, you might work an increase or decrease every 4 rows or so. In the bust area, we don’t have room for gradual increases so you will need to increase every row.
You want your vertical darts to fit over the center, high point of each breast, so try on your sweater and place a stitch marker where you wish to add your darts. As you are knitting work your increases and decreases on either side of that stitch marker. The number of stitches you will want to add for the darts will depend on your bust size and will vary from person to person. You will first work the increase (one on each side of the two markers, every row until you have increased your desired number of stitches), then knit an inch or so without increases or decreases, and then work the decreases so in the same manner (one on each side of the stitch marker, every row) until you have decreased out your desired number of stitches. This will create a cup of sorts. Be sure to use the proper slant of increases and decreases to avoid leaving holes in your fabric. I recommend using lifted increases and for decreases use ssk and k2tog.
Choose the method that works the best for you and you’ll be on your way to knitting an amazing, custom fit sweater!