Adjust pattern size

How do you adjust pattern size, for example a short bolero with pattern written in chest size 33 and 39 (but person has chest size of 36)?

You can use larger needles and knit size 33, or smaller needles and knit size 39. Or figure out the number of stitches between the two sizes and split the difference. For instance if the CO for 33 is 70 and the one for 39 is 80, then CO 75.

Another thing, is it snug or loose fitting? If it’s supposed to be loose, then 39 might not be too big. Sizing sometimes isn’t what size you are, but what size the finished product will be and if it’s meant to be loose, then it might be okay for you.