Many of the terms in the printing industry for weights and measures have always been confusing. How paper weight in pounds or thickness in points is determined takes understanding paper basis weights and point measurement.
A 10 pt. paper stock will be similar to an 80-pound cover stock but it will not be 80-pound itself because the parent sheets of each are a different size. Point stocks are used for things like postcards, portfolio folders, direct mail pieces and inkjet photo printing paper, where the thickness of the paper is the most critical factor in selecting them.
Most printing papers have weights -- such as 20-pound or 60-pound -- based on their basis weight. Basis weight is determined by the weight of 500 sheets of their parent sheets. Parent sizes are the largest size sheet available for the type of paper. Different paper types have different parent sizes adapted historically to run on different size printing presses.
Point stocks are a different form of measurement based on the thickness of paper. Thickness is important for things like meeting postal minimum thickness requirements for direct mail, printing packaging and other items where durability depends on paper thickness. Usually the weight is not included in specifications, but details about basis weight are available from a paper merchant or manufacturer on request. Point measurement for paper thickness, where 1 point equals .001 inch, is not the same as point size for type and other printing measurements.