Help please,fisherman’s rib

Hi% I am knitting a King Cole pattern, no 4453, which is done in half fisherman’s rib.
I have changed it to proper fisherman’s rib, which obviously means I am using more wool and knitting extra rows.
My questions are

  1. after the armhole decrease on front and back, the pattern says to work 45 rows, but doesn’t give a measurement. How many rows will I need to do?
  2. Sleeve increases, for the size I’m doing, it says to increase every 8 rows. To allow for the extra rows, should I increase every 10 or 12 rows?
    As I’m knitting this for a very tall young man, I am having to add in an extra 3 inches on both the overall length and the sleeves.
    I hope you can help.
    Thanks

You can calculate the measurement from the row gauge given for the pattern, 38rows/4inches. At that gauge, 45 rows would be about 4.75inches. You can then figure out how many rows that means using your row gauge measured on the body of the sweater.
You can figure out how to space the sleeve increases knowing how long you want to make the sleeves for this tall young man. Knowing your row gauge will let you space out the increases.
This video takes into account the cuff length as well as the length without increases at the top of the sleeve. It’s long but Roxanne goes through the calculations and it’s worth it to get the width and length you want. I’ve also seen this worked out on knitter’s graph paper.
https://www.youtube.com/watch?v=vTQ5O_R3bIc

Thank you so much. That makes life a lot easier.