The way we identify paper here in the USA frustrates many people. Most of the world utilizes the metric system but here in the US, we use use a nomenclature related to the manufacturing process. After reading this article you’ll be able to differentiate paper by types, thickness, weight, application, finishing and use. You will be able to compare how paper in USA is identified elsewhere.

 

You will be able to answer questions such as “How is a 20# ( pound ) copy bond paper different from a 60# offset paper?”

 

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All About Paper Weights: Understand "Basis Weight", Bond, Book Grades, Text Grades, Cover Stock, Index and Tag.

("U.S. Basis Weight") is defined as the weight of 500 sheets of paper in its basic production size (parent size), before any cuts take place. Find the chart of paper manufacturing sizes on this same page.

  • Example #1: Basis Weight of Bond Paper: A sheet of bond paper comes out a of production line and measures 17x22 inches. If the weight of 500 of those sheets is 20lbs, that bond paper will get to be identified and labeled as “20lbs”, or “20# bond”. When you cut the 17”x22” sheet into two, you will get 2 sheets each measuring 8.5”x11” which happens to be a “letter size”. Assuming that we have those 500 uncut sheets, we’ll end up with 1,000 sheets of 20# bond paper. Each group of 500 sheets then weights 10 lbs.

    Conclusion: The Basis Weight of Bond paper is 20lbs.

    If the same components to the paper and thickness were produced out of a sheet of paper that measures 25 x 38 inches, 500 sheets of that paper would weight 50 lbs. It would be a 50lbs basis. So as you can see, the paper, physically, would be the same one. But its name will be 50 instead of 20. The number itself is not indicative of how thick one paper is when compared to another one.
     
  • Example #2 for 100 lbs coated paper: We will find out the basis weight of a coated sheet of paper. There is an illustration that helps visualize. Coated paper is manufactured in sheets of 25 x 38 inches. In this case, 500 of those sheets weight 100 lbs. Therefore the Basis Weight for this paper is 100 lbs, also known as 100# coated text paper.
This is a picture of a skid of paper. There are annotations on the image as card card-body. The manufacturing size is 25x38 inches and in the picture there are notes that help understand how to know the basis weight
 

Chart of Paper Manufacturing Sizes to determine Basis Weight Parent Sizes

Paper TypeManufacturing Ream Size (Parent Size) inchesManufacturing Ream Size (Parent Size) ISO - mm
Bond (Copy Paper, Ledger, Manifold)17" x 22"432 mm x 559mm
Book or Text(Coated Gloss or Coated Dull or Offset Paper)25" x 38"635mm x 965mm
Bristol22 1/2" x 28 1/2"571mm x 724mm
Cover (Glossy cover stock or uncoated cover stock)20" x 26"508mm x 660mm
Index

25 1/2" x 30 1/2"

648mm x 775mm
Newsprint (Tag)24" x 36"610mm x 914.4mm

Paper is manufactured at paper mills using different machines with different technologies.

There are several stages in the manufacturing process being finishing the last one. Wood chips get transformed into pulp, rollers calender the paper and determine the thickness of the paper.During the production and finishing processes the softness is determined. For glossy or satin paper, a coating gets added to complete the process. Therefore different machines in different widths produce different types of paper. The end product at the mill is a roll that gets trimmed into flat sheets into what is known as the parent size.
Paper is manufactured in rolls. Rolls are then extended on tables and cut to sheets. Different equipment and grades produce different widths of rolls.

Names and Sizes of Paper in the US Standard System

The way to obtain different sizes of paper is by cutting the parent size into fractions. The typical way is to cut the mother sheet in half.

U.S. Standard

DesignationmmInches
Ledger279 x 43211 x 17
Legal 8.5 x 14
Letter216 x 2799.5 x 11
Monarch 7.25 x 10.5
Executive140 x 2165.5 x 8.5
Statement108 x 1404.25 x 5.5
Business Card 2 x 3.5

The U.S. Standard System changes the proportions of the sheet once it is cut in half making it difficult to size up or down

The International Systems for paper weight and sizes is designed so that cutting paper in half still keeps the same proportions. That system is known as ISO "A"

The Grades of Paper are defined in terms of its use. Each grade serves a purpose:

  • Opaques and Offset Papers
  • Coated Papers
  • Writing Papers (a.k.a. Correspondence Papers or Bond Papers)
  • Text and Cover papers

Opaques and Offset Uncoated Papers: These are similar with some specific differences

Offset uncoated papers are commodity papers available in large volumes. Over the years, a change in formulations made it alkaline as opposed to acidic, which gives it better archival properties. Their internal bonding is good, with high surface strength and dimensional stability.

Offset Paper: Typical basis weight for this paper are 50 lbs, 60lbs, 70lbs and 80lbs

The finishes of offset papers are
  • Smooth
  • Vellum finish which is extremely rough
  • Patterns: as in Laid and Linen finishes

Opaque Paper: The typical basis weights for opaque paper are 50 lbs, 60lbs,70lbs and 80lbs

The quality of pulp use is better so it has higher opacity than offset paper (which means less see-through) #Opaque is also more expensive than offset grade. The finishes of opaque papers could include a very light clay layer giving it a very high quality.
  • Satin
  • Film Coat
  • Thin Coat

Coated Papers Have 5 types of Finishing and 5 Qualities

Coated Papers are made like offset papers but have a clay coating added on their surface before calendering. The coating creates a gloss or sheen on the its surface. This coating holds ink better and helps get a smaller dot that in turn produces a better printing quality. The clay often accounts for as much as half of the weight of the paper. Therefore the quality of the clay determines how bright, printable and strong the paper will be (resistance to tear, shear, etc)
The calendering process on coated paper produces the following types of finishes
  • Cast Coated, which are very shinny
  • Gloss
  • Dull
  • Silk
  • Matte
The quality is determined by the brightness, smoothness, mechanical properties (resistance, shear, etc) and stability of thickness among others. Paper is rated from 1 to 5, 1 is the highest quality. 5 is the lowest quality

Writing Paper, Correspondence Papers or Bond Papers

This writing grade, historically called bond paper is designed for letterhead, corporate identity and home desk let printers or office printers. Bond paper performs card card-body for handwriting. It can be omprinted with a watermark or can include have cotton fiber to provide an elegant feel and mechanical strength.

Text and Cover Papers

These are premium uncoated papers that are available in an amazing variety of colors and finishes. Some text papers are lighter while cover papers are thick and nice for covers, brochures and business communication.
Basis weight that are equivalent
US Basis WeightsCaliperMetric
BondTextCoverIndex1 Point = 0.001"GSM (g/m2)
2050   75
2460   90
2870   105
3280   120
369050  136
3810055 6.0140
431106090 162
4712065978.0177
54 74110 199
58 8012010.0218
  90135 245
  9314012.0253
  100150 271
  13020016.0350