It would be great to have internationally standardized pallet sizes in order to optimize the total capacity of a carrier, but the standards are far from universal. There are, however, several common sizes of pallets:

40” x 48”                Similarly: 1000 mm x 1200 mm; these are most common across the world

42” x 42”                Common in North America, Europe, and Asia

45.9” x 45.9”         Common in Australia

43.3” x 43.3”         Common in Asia