There are 8 Ounces in a cup. Therefore the Tablespoon is 1/2 Ounce. A teaspoon is 1/3 of a tablespoon or 1/6 of an ounce. Remember this, 128 ounces in a gallon. 1/2 of a gallon is the next stop down = 64. 1/2 of that is a quart = 32 ounces. 1/2 of that is a pint = 16 ounces.
The difference between US Letter and Legal Paper sizes and international A4 is discussed here, however it is important to say that Letter is effectively the equivalent to A4 size in the USA.
The ISO standard paper sizes are not commonly used in the United States and Canada. Instead paper formats like Letter (8.5 x 11 inches), Legal (8.5 x 14 inches), Executive (7 x 10 inches), and Ledger/Tabloid (11 x 17 inches) are widely used.