A standard sheet of paper measuring 8.5 by 11 inches weighs 0.16 ounces. Knowing the weight of paper is useful in applying the correct postage to a letter, as the US Postal Service charges for postage based on the number of ounces being mailed.
Factoring in the weight of the envelope, it is possible to mail five pages of letter-sized paper and still pay the lowest possible postage for up to one ounce. One may mail six additional pages in the same envelope and only have to pay for one additional ounce of postage.
Numerous thicker paper formats are available, including paper commonly used to print books and covers. When working with these types of paper, calculating the total weight of a document is essential to determine the correct postage.