If, after this thread, you are totally confused and haven't got a clue, then just buy 4 yards of double-width material and take it to your kiltmaker and just ask. If you are a seriously hefty guy, like with a waist measurement over 48-50 inches, then buy 5 yards. You might spend more money than you need to, but then the leftovers might make you a fly plaid or make your lady a nice scarf or sash.