Sweater sleeve help

I haven’t gotten to the sleeves yet but I realized that the pattern when knit is a 1/2 sleeve sweater which I would consider short for a sweater. I want to make it so that it is a full sleeve sweater. For that, I think I will need to add 1 fair isle panel and 2 areas of
1 row striping in garter stitch and 1 6 row stripe in between the fair isle panels(all are 6 rows except for the top stripes before the thick white stripe(bust increase area) and all pattern repeats in the fair isle panels are multiples of 6 stitches) and have everything match the pattern on the sweater. I know how much ribbing in rows I need for an inch on size US 6 needles. But will this be sufficient to get a full sleeve sweater or will I need more rounds?

Here is the address for the pattern I am working on:

http://knitty.com/ISSUEdf13/PATTsophialoren.php

Very nice fair isle pattern!
There are two things you can do.
One is to add up all the rows and use the row gauge (rows/inch) to estimate the length.
The second is to measure the actual length of those pattern repeats on the body of the sweater. This is going to give you a more accurate measure, of course.