For mail forwarding purposes a "package" is defined as follows:

U.S Domestic destination:
Anything weighing more than 2 pounds OR anything larger than 12 x 14 inches.

Canadian destination:
Anything weighing more than 1 pound OR anything larger than 12 x 14 inches.

Worldwide destination:
Anything weighing more than 6 ounces OR anything larger than 12 x 14 inches.