How many square feet on a pallet

R15 16 o/c = 1080 s/f per pallet R15 24 o/c = 1080 s/f per pallet R21 16 o/c = 720 s/f per pallet R21 24 o/c = 720 s/f per pallet

Both 16" and 24" on center batts cover the same amount of square footage for the relative R values.  So, whether your studs are 16" on center or 24" on center each pallet of R15 will cover 1080 square feet and each pallet of R21 will cover 720 square feet