Choosing the right size to knit is one of the most important things you can do! By 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.
This will give the shoulders, neckline, and everything except the bust area has the absolute best fit. Using the full bust measurement your bust will fit but it is very likely the rest of the sweater will be too loose.
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 hips. I also highly suggest adding lifelines throughout your work so you can double check the fit as you go. Especially at key areas such as pre/post shoulders, armholes, bust, and waist.
In most of the patterns, I design the size range increments by 2″ from size 32 to 46. I suggest you drop down to the smaller size if you fall in-between one of these sizes. So for example, if you have a 35″ high bust measurement you should make the 34″. Since knitted fabric has stretch to it I find rounding down to the smaller size gives a better fit.
If you want 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.