Those Tricky Paper Weights

Definition of Weights

Stock designations in printing can be very confusing. For instance, a printer may use 60# offset stock for letterhead or a 24# bond stock. In actual fact, 24# bond, and 60# offset weights are approximately the same. But the offset stocks are generally for full color printing, while bond stocks are more often used for one and two color printing.

Caliper refers to the thickness of a sheet of paper expressed in thousandth of an inch. This measurement is taken with a gadget called a micro meter. Normally, paper caliper should not have more than a + or - 5% variance within a sheet.

It isn't practical to talk about the weight of a single piece of paper, so the 500-sheet ream is the unit that has been chosen for comparisons. Americans designate by "basis weight" which is calibrated on how much a ream of that particular paper weighs when cut to it's basis size. The basis size varies by category of paper.

Most of the rest of the world generally designates "grammage" which is grams per square meter. .

Paper weight is sometimes stated using the "#" symbol. For example, "20#" means "20 pounds per basis ream of 500 sheets".

To confuse the issue even more, paper is generally designated by weight while cardstock is designated by thickness.

Definition of terms

Grain: When printers are designating paper, they also take into account which direction the grain is running which is the direction most fibers lie in a sheet of paper. For example, with bottle labelling it is essential that labels are produced with grain running left to right, otherwise the labels might peel off the bottles. Grain direction can and does have an effect on some laser printers, so its best to be aware.

Regarding the terms in the chart below:

Bond paper: writing paper and reprographic paper used for letterheads and business forms. It is manufactured at 17" x 22" and cut down from there. (It's name is derived from the original use of such paper for government bonds.)

Offset paper: more resistant to water than bond so it dries quickly and less susceptible to "picking" (Where tiny bits of the surface of the paper may come off while printing).

Cover weight: generally used for the cover of books, pamphlets, or other soft covered books.

Tag: strong, heavy paper calendered (flattened) to a smooth hard finish.

Index paper: heavy, stiff paper characterized by bulk and strength; includes index and printing bristols.

This chart will help you sort out how the designation of one category of paper compares to another.

The blue numbers indicat the most common weights offered in each category.

 

Weight and thickness equivalents for paper stocks

Bond	Offset	Cover	Tag	Index	Points	Thickness
Lbs	Lbs	Lbs	Lbs	Lbs		Inches

16	40	22	37	33	3.2	.0032
20	50	28	46	42	3.8	.0038
24	60	33	56	50	4.8	.0048
28	70	39	64	58	5.8	.0058
29	73	40	62	60	6	.0060
36	90	50	82	75	6.8	.0068
43	110	60	100	90	7.4	.0074
47	120	65	108	97	8	.0078
53	135	74	122	110	9	.0085
54	137	75	125	113	9	.009
58	146	80	134	120	9.5	.0092
65	165	90	150	135	10	.0095
67	170	93	156	140	10.5	.010
72	183	100	166	150	11	.011
76	192	105	175	158	13	.013
82	208	114	189	170	14	.014
87	220	120	200	180	15	.015
105	267	146	244	220	18	.0175