Description of Paper Weights

However, the unit-weight of paper is more generally expressed as its BASIS WEIGHT . . . the weight, in pounds, of a ream of specified dimensions and sheet count. Thus, regardless of the actual size of the sheet, the size and count of the ream-standard upon which the basis weight of the sheet is calculated must be stated. A 30-pound basis weight sheet in the fine-paper field - where a 17 x 22 - 500 ream would apply - is logically not the same actual weight as a 30-pound basis weight sheet in the coarse-paper field, where the ream standard is 24 x 36 - 500.

Although not readily apparent, there was a logical reason for the adoption of this motley conglomeration of ream standards. Most of them developed when the industry was less conscious of mathematics and more conscious of the weight of a sheet mold. When papermaking was a handcraft, and paper was fabricated one sheet at a time, the sheet mold size determined the sheet size.

Sheets 17 x 22 lent themselves to cutting into four 81/2 x 11sheets, the standard for business stationery. Thus the 17 x 22 ream became the established unit of quantity for writing papers. The 25 x 38 book-paper ream developed because such a size could be trimmed handily into sixteen 6 x 9 book formats, without significant waste.

The first newsprint presses printed a sheet 2 x 3 feet, and the ream size for newsprint became 24 x 36 - 500. Newsprint was made from groundwood pulp, and hanging paper (Wallpaper) was made on newsprint machines. Newsprint was used as wrapping paper, and the first paper bags were made from newsprint. The 24 x 36 - 500 ream size (3000 square feet) became standard for packaging papers, even though kraft pulp rather than groundwood was used to get greater strength.

The rest of the world, including England which originally blessed us with this system, has gone metric and uses grams per square meter as the standard basis weight of all types paper and paperboad. Converting to gsm would be a step in the right direction but old customs die hard.

Bond, writing, ledger	17 x 22 - 500
Manuscript cover	18 x 31 - 500
Blotting	19 x 24 - 500
Box cover	20 x 24 - 500
Cover	20 x 26 - 500 or 1000
Bristol and tag	22.5 x 28.5 - 50
Tissue	24 x 36 - 480
Newsprint	24 x 36 - 500
Hanging, waxing, bag, etc.	24 x 36 - 500
Book and offset	25 x 38 - 500
Index bristol	25.2 x 30.5 - 500
Paperboard (all types)	12 x 12 - 1000 (1,000 square feet)

Note: We have had many inquires concerning paper weight, the evolution of basis weights and sizes, how certain sizes became standard, etc. Charles P. Klass was good enough to update his "Description of Paper Weights" and give The Paper Industry Web permission to post his article. We are grateful to Mr. Klass for this courtesy.

DESCRIPTION OF PAPER WEIGHTS