Letter (paper size) "official" "Government Letter" size, , was used in government, while paper was standard in most other offices. In the U.S., paper density is usually measured in "pounds per ream" (of 500 sheets). Typical Letter paper has a basis weight of paper of – the weight of 500 sheets (a ream) of paper at and at 50% humidity. One ream of 20-pound Letter-sized paper weighs , and a single Letter-sized sheet of 20-pound paper weighs , which is equivalent to 75.19 g/m. Some metric information is typically included on American ream packaging. For example, 20-pound paper is also labeled as 75
Paper size the sheet of paper is folded in half widthwise, let "c" be the length of the new short side: "c" = . If we take the ratio of the newly folded paper we have: formula_3 Therefore, the aspect ratio is preserved for the new dimensions of the folded paper. Weights are easy to calculate as well: a standard A4 sheet made from 80 g/m paper weighs 5 g (as it is of an A0 page, measuring 1 m), allowing one to easily compute the weight—and associated postage rate—by counting the number of sheets used. The advantages of basing a paper