I'd say "enough pleats for what?" Who says how many pleats are enough? Historical accounts I have read indicate that there was no standard length for a belted plaid, but that it tended to range from 3 to maybe 6 yards, with 4 being the average.

I've worn a 4 yard belted plaid many times with no trouble at all. I've a 38" waist, 44" hips, and stand 6' 3" tall.

Consider this... the belted plaid (feilidh-mor) became the feilidh-beag, which became our modern tailored kilt. And the earliest tailored kilts we know of all contained around 4 yards of cloth. It wasn't until the mid-nineteenth century that excess yardage was regularly used.

For the belted plaid, ideally you want the fabric wide enough to go from your knees to the top of your head. In today's tems "double width" fabric refers to anything 54" wide or more, which is usually sufficient unless you are extremely tall. Traditionally, it meant seaming two lengths of 25" to 30" wide cloth together. If they cloth you are working with is only 45" wide, I'd cut it into two 30" wide strips and seam those together to make a single 60" wide peice.

I'd go ahead and make it 5 yards long to begin with. You can always cut some off if you feel it is too much. That's a better than having to add more on later!