My pattern calls for casting on 130 st for a one size fits all vest.
How many additional sts do I need for a 2 or 3x? I’m not sure how to figure this out. The pattern is for the Jiffy vest where you wrap the yarn 3 times around the needle for every K st. Then on the next row you drop the extra wrap around.
Do you have a link to the pattern?
Generally, you can figure that 130 stitches will equal X number of inches. Decide how many inches you want yours to be and do a bit of math.
Or look at the gauge of the pattern and figure how many stitches it would take to reach the measurement you want.