How to find the right size for you?
Measure yourself around the chest and add the number of cm you want for preferred range of motion. To get the right width for my use, I usually measure around the chest and add 10 cm. Then there is plenty of room for wool underwear and the sweater fits well. Remember that the stated size is only achieved by following the stated knitting strength. The length of the sweater is standardized, so here you can measure the length of a garment that you think fits well and adapt to your body.
NOTE: pin size is for guidance only. If you get more stitches than stated on 10 cm, go up a needle size. If you get fewer stitches than stated on 10 cm, go down a needle size. Check the knitting tension of the pattern. Remember that many knit tighter on pattern than on plain stockinette stitch. If you are measuring knitting strength on plain knit, you should measure again on the pattern, and possibly change Pinne if necessary.