You don’t need to buy a postage scale or drive to the post office to calculate the exact weight of a letter or manuscript. All you need to know is the weight of a single page—then multiply by the number of pages.
        What does 20-pound paper mean? Surely, a ream of copy paper doesn’t weigh twenty pounds. The term refers to the substance weight of a standard ream.
        A standard ream consists of 500 17” x 22” pages. These are cut lengthwise and crosswise to make four reams of 8 1/2 ” x 11” copy paper. So a ream of 20-pound paper weighs five pounds.
        Converted to ounces (5 times 16), a ream weighs 80 ounces. If you divide 80 by 500, you get 0.16. Postal rates will change, but a sheet of 20-pound paper will always weigh sixteen one-hundredths of an ounce.         A lot of people waste money on letters because they guess the weight by the “feel,” and often stick an extra stamp on to be safe. It may seem hard to believe, but a five-page letter on 20-pound paper can go for only one ounce. The paper will weigh 0.8 ounces (5 x 0.16), and a business envelope weighs almost exactly the same as a sheet of paper. (Open one at the seams and spread it flat and you’ll see.) So if you add another 0.16 for the envelope, you end up with 0.96, still under one ounce. 
        

    
        There are some caveats, however. First class postage can only be used for items that are smaller than 6 1/8” high by 11 ½” long, and cannot exceed 3.5 ounces. They must be less than a quarter   inch thick.

        If you want to mail a 10-page manuscript, multiply 10 by 0.16 and you get 1.6 ounces. A 9” x 12” manila envelope weighs a fraction under one ounce. But here’s where the fun comes in. The postal rates change when the size of your envelope exceeds 6 1/8” x 11 ½”. And additional conditions apply.  Items in this “large envelope” category cannot exceed 12” by 15” and cannot be more than ¾” thick. The most interesting conditions for this group of mail is that it must be uniform thickness and it must be flexible. Flexibility  is in the fingers of the postal employee.
    

    
        Some people waste money because they don’t know that additional ounces are much cheaper than the first ounce.  For both small and large envelope pricing (44-cents and 88-cents), additional ounces are only 17-cents.
        Postal rates will change. That is one of life’s certainties. But if you know the weight of a sheet of paper and an envelope, and you understand the rules, you can save yourself some money.
   
  
                     Copyright © William Arthur Delaney