Add approximately 4" to either the width(W) or depth(D) for a loose fit.
For length, add half of depth to actual length.

Example - a loaded pallet measures (W)46" x (D)49" x (L)50".

To properly size the pallet cover, you do the following -

(W) 46" + 4" = 50"

(D) 49" = 49"

(L) 50" + 25" = 75"