Here's how to figure it out, roughly.

You're going to have 8 yards of fabric, we'll assume. Let's say that the sett is 6 inches. It won't be (probably) but you can repeat these calculations with your numbers.

6 inch sett means that in a yard there are 6 setts, right? 6 x 6 = 36

OK, assume you'll need a full yard for the over-apron, the under-apron pleat, and the fringe. Assume you'll need another yard for the kick pleat and the under-apron. That leaves you 6 yards for the pleats, right?

If you have 6 yards, and there are 6 setts per yard, then you have 36 "setts-worth" of cloth to work with. But if you make 3/4 inch deep pleats, and you pleat to stripe which is a good size, then we've already figured out that you'll have 30-31 pleats and use up 30-31 setts of cloth.

Conclusion, you have enough cloth to pleat to the stripe and have 3/4 inch pleats, which is a very traditional-looking kilt.

What if the sett is 8 inches?

Again, assume you'll need a full yard for the over-apron, the under-apron pleat, and the fringe. Assume you'll need another yard for the kick pleat and the under-apron. That leaves you 6 yards for the pleats, right?

If the sett is 8 inches, then there are 4.5 setts per yard. You have 6 yards.

6 x 4.5 = 27 so you have 27 setts worth of cloth to pleat up to go over your rumpus.

We already saw that a 7/8 pleat reveal gives you 26.28 pleats, right.

So you could TRY to split 1/16th inch hairs (waste of time IMHO, others may differ on this) and try to make pleats with a

23 inches split divided by 27 pleats = 0.851851 inch wide pleat...or you could realize that fitting a kilt is not an utterly exact science, make 26 pleats and ooch the thing up or down on your waist an inch or so until it buckled right.