I use just about exactly a yard of canvas for one kilt. Four strips do a perfect job - two strips for the apron and underapron canvas, and two for the pleats. So that I don't waste any canvas, I first measure how deep the canvas needs to be in the pleats (say 6 1/2"). I cut two strips that are 6 1/2" each and save them for the pleats. Then I split what's left (the canvas is 24" wide, so that leaves 11" to split, giving me apron and underapron canvas 5 1/2" wide).

I cut the pleat strips first, because that's the part where the strip width is critical. I use whatever is left over for the apron and underapron. For example, if the pleats needed 7", I'd split the remaining 10" and use strips only 5" wide for the apron and underapron. That way, I don't waste canvas.

Before I adopted this strategy, I used to wind up with stripes 3-4" wide that weren't good for anything.