Usually, a box pleat will use less material than a knife pleat. About half has much in fact. so, with fourteen yard (if double width) you could make 7 box pleat kilts or 4 knife pleat kilts (if you use only 7 yard per kilt, which is not that much, unless you go for shallower pleats)

Then again, some here have better knoledge than me and will answer soon enough... ;o)

Have fun....

Ooops, I've counted 4 yards instead of five for the box pleat kilts... my bad...