How many sheets of paper can i mail with one stamp?

Answer:    I have found that you can mail four 8 1/2" x 11" sheets of paper in a 4 1/8" x 9 1/4" envelope for a $0.39 stamp.
Postage is determined by weight, not number of pages, so obviously it depends on the size and weight of the paper. Usually the equivilant of five normal sheets of 8 1/2" x 11" paper will weigh just a hair under one ounce, which is what you can mail for 39c within the United States - each additional oz is another 24c. If you use an envelope, rather than stapling the pages (like for a newsletter), count the envelope as one sheet - so 4 sheets plus an envelope is usually okay. To be absolutely sure, take it to the post office or someplace else with an accurate scale.

If you are mailing to or from a country other than the U.S., you need to know the correct rate for that country.