Which paper is thicker: 28-pound (28#) bond/writing paper or 50# uncoated offset stock? It may seem counterintuitive, but the 28# bond is thicker!
Why? Paper is measured either in pounds per 500 sheets (one ream of paper) or in pounds per 1,000 sheets (see below) of a standard size of sheet based on the group or category of papers being graded. The different types of grades are Bond, Book, Text, Cover etc. Each group of the grade of paper is assigned a standard size that all weights are referred to. The basics of this standard are as follows:
Bond has a standard size of 17 x 22" and this is the size that is measured for 500 sheets. If 500 sheets of this size weigh 20lbs., then the paper is classified as a 20lb. bond. Heavier and lighter stocks will obviously be thicker or thinner than the 20lb. Therefore 16lb. Bond or 24lb. Bond will be the variations on this.
Now the confusion... the weight of 500 sheets of the standard sheet size (also known as the basis size) is commonly known as the paper's basis weight and is always noted as a weight in lbs.
This can be confusing! Here's why.
A sheet size different than the above is calculated as a fraction or multiple of the basis weight and is normally noted for 1,000 sheets rather than 500. The weight thus calculated of the acutal sheet size is always noted in weight per thousand (M in roman numerals) and therefore said to be 19 X 25" - 100M meaning that 1,000 sheets of 19 x 25" will weigh 100 lbs.
Bond stocks (often referred to as "Writing") traditionally are uncoated stocks and are normally used around the office such as letterheads, photo copier and laser printer paper. The standard weight utilized is 20lb., with 24lb. being the heavier alternative, and 16lb. being the lighter alternative.
If 500 sheets of Bond paper (17 x 22 inches) weigh 20 lbs, then a ream of paper cut to Letter size will be labeled as 20 lb.
Writing is a grade similar to bond, but made with a shorter fiber, yielding a softer sheet which can be made with a variety of finishes and which accepts ink more readily. Writing is generally more expensive than bond and is used for higher end applications like company stationery. Some bond and writing papers have distinctive watermarks in the sheet.
Uncoated offset is made specifically for the rigors of commercial offset presses and is often used for the same applications as bond.
The basis size of bond/writing papers is 17 x 22", whereas offset papers is 25 x 38".
Equivalent bond/writing and offset weights:
16# bond or writing=40# offset
20# bond or writing=50# offset
24# bond or writing=60# offset
28# bond or writing=70# offset
32# bond or writing=80# offset
Both Coated and Uncoated stocks are available under the category of Book Papers. Weights vary from 30lb. bible stock (very thin - mostly utilized for bibles) to a maximum around 115lbs. This classification is the most common for posters, catalogues, booklets and publication magazines.
The basis size of Book papers is 25 x 38"
Gaining on quality above the book grades, Text stocks are utilized in projects requiring a better grade of paper and usually range from a low of around 60lb to a high of 100lb.
The basis size of Text papers is 25 x 38"
Cover papers, as the name denotes, is heavier and is utilized for post cards, business cards, rack cards, door hangers etc. The ranges of weights for Cover are from a low of 60lb. to a high of 130lb.
The basis size of Cover papers is 20" x 26"
To determine equivalent thickness, use the chart below to convert between paper types.