When knitting a sweater there are many things to consider but one of the most important things you can do is make sure you have chosen the right size to knit! If you are following the wrong size then all your hard work will only end in tears when it doesn’t fit.
Always choose the size based off your high bust measurement.
High bust measurement is the measurement taken directly below your underarms and will run above your bust. (Full bust measurement would have been taken lower down, across the fullest section of your bust.)
You should use the high bust measurement because this will give the shoulders, neckline, and every single thing except the bust area has the absolute best fit. If you used the full bust measurement instead then while your bust will fit it is very likely the rest of the sweater will be much looser than it should be.
Now that you have the overall fit sorted you can add any alterations later on, such as short rows, to accommodate for a larger bust or even hips!
In most of the patterns I design the size range increments by 2" from size 32 up to 46. If you fall in-between one of these sizes I suggest you drop down to the smaller size. So for example if you have a 35" high bust measurement you should make the 34". I prefer fitted sweaters and since knitted fabric has stretch to it I find rounding down to the smaller size gives a better fit.
If you want a bit of a looser fit rounding up to the larger size might be a better option for you. So using the same example of a 35" high bust you would knit the 36".
As long as you are going by the high bust measurement you are on the right track to a successful fit!
If you are still unsure about what size you should knit please let me know, I'd love to help.