Help with increase pattern width

Hi there,

I’m a fairly new knitter and found this blanket I’d like to knit - however I’d like to make it bigger. I know I can follow the pattern and knit it just fine, but I have no idea how to increase the pattern. I was wondering if anyone here would be able to help.

The blanket I’d like to knit is this:

Basically, what I’d like to do is knit an extra rib and cable - so have it go cable, rib, cable, rib, cable. But I have no idea how many stitches to cast on or how to alter the pattern.

Any help would be greatly appreciated! Thanks so much!

Great looking throw!
Add on an extra 26 sts for another rib and cable. That’s 18sts for the pattern between cables and 8sts for the cable. Cast on 86sts.