It is very rare when a sewing pattern will fit you right out of the envelope. The patterns are drafted with “standard” measurements in mind. But chances that someone actually falls right into those standard measurements are very little. The Bessie top is drafted with quite a bit of ease through the waist and hips, so hopefully, you won’t need to do much grading between sizes.
First off, I recommend that you chose the size based on your bust measurement, as it is the most fitted area of the top. You can check out Anna-Zoe sizing chart here to see what size would fit you best.
For example, let’s say your bust falls into size 16, but your hips fall into size 14. You could make a straight size 16 and call it a day. Or you could grade the pattern down from the bust and see if you like that fit better.
To grade the pattern between the sizes, print off the sizes you need by selecting size layers on the PDF file. If you are not sure how to use PDF layers, check this tutorial out. It uses a baby pattern as an example, but the idea is the same.
Next, grab a pen and a ruler.
To grade down from the bust, as in the example above, draw a line from the lowest dart leg at size 16 and down to the hem of size 14.
Repeat for the back pattern, and you are done!
Let me know if you have any questions.