Little help?

If I were to knit a large Afghan with super bulky weight yarn, and 2 stitches equals one inch I would need 1283 yards which is approximately 6 skeins. But that’s stockinette stitch. Now if I were to use pearl brioche. Would I need one extra skein or two? For safe measure?

The best way to determine this is to knit a good sized swatch in the pattern stitch and weight it to determine how many yards were used. You can then scale up to the area you need plus an extra skein.