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.
But for office or home use, the standard is the three-drawer and four-drawer type, which comes in either letter-size or legal size paper. By letter-size and legal size, we mean the width of the filing cabinet. They also come in different depths. They may be 25, 26 1/2, or 28 inches deep.