I'm writing the book 'How to grade a bra and brief' and one of popular questions I receive about grading is: how to apply the grade to the pattern, and which point to alter if you need to increase or decrease the final measurements to get the grade measurements.
In an ideal world if you needed to grade the bra size by the width 1.2cm you would add 6mm to one side and 6mm to the other side of the cup to achieve the increase in bra size by 1.2cm.
However because you on some points increasing the points upwards as well, your increase of the pattern (or the increase going up a bra size) may not reach 1.2cm.
So which point of the pattern should you increase more to get your desired measurement you want?
As the breast and bra size gets bigger, then the design of the bra needs to do it's job and support the heavier part of the breast which is the outer part (near underarm) and project them forward.
Therefore if your measurements are falling short I always increase the outer points on the bra (see picture) this then prevents the flattening of the breast and so you don't end up wearing your boobs under your arms.
If you are coming up measuring over (your 1.2cm increase is more than 1.2cm) your grading measurements, then I would go in reverse, and decrease the CF part of the bra.