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 Legal sized papers are the common size papers in the US, called as the Legal size paper (US Legal). The paper is 8.5 inches by 14 inches (around 21.5 cm by 35.56 cm). If someone tries to enlarge a document from the letter to legal, they may lose the information and the alignment will change.