Paper comes in all thicknesses, sizes, and colors. Color is fairly straightforward, but size and thickness are a bit more complex.
In the United States, paper comes in standard sizes with dimensions expressed in inches. In most of the rest of the world, paper comes in numbered sizes with dimensions expressed in metric units. The majority of countries developed a standard for paper sizes during the early 20th Century, and the international standards organization (ISO) has formalized these measurements (ISO 216:2007). The standard designates two series – A and B. Both A and B series define numbers for each paper size. Each number in the the A and B series represents a halving of the next value. Smaller numbers represent larger sizes (A0 = largest, A10 = smallest). For example, two A6s equal an A5.
This table summarizes popular U.S. and Metric paper sizes (series A):
Paper also comes in various thicknesses. Just like paper sizes, thickness can be expressed in standard (U.S.) and Metric units. Also like paper sizes, the Metric system makes more sense, because all thicknesses are expressed in the same base unit, grams per square meter (gsm). The U.S. thicknesses differentiate between regular paper and card stock, which is thicker (like index cards). Additionally, each common thickness can be expressed as bond or offset. For standard copy paper in the U.S., these are equivalent …
- 20 pounds (lb) – bond
- 50lb – offset
- 75.2 gsm – metric
While researching for this post I learned for the first time how 20lb and 50lb can be equivalent. Bond paper weights are determined by weighing 500 sheets of full-size paper (17 x 22 inches), with the thickness as a factor. Five hundred full-size sheets of standard copy paper weigh 20 pounds. Offset paper uses dimensions of 25 x 38 inches as a full-size sheet. As a result, 500 full-size sheets of standard copy using offset specifications would weigh 50 pounds.
Another category of thicknesses is “cover” weight. These are the thicker papers necessary for sturdier printing (posters, business cards, etc.) and index cards. The full-size dimensions used as the basis for cover weights are 20 x 26 inches.
A much easier system is the metric method of measuring paper thicknesses. All measurements are expressed as grams per square meter (gsm). While U.S. measurements are based on 500 sheets of paper, calculating gsm is based on the weight of one sheet of one large sheet (1m x 1m or 39.37 inches squared).
This table summarizes common paper thicknesses.
The table below summarizes weights of popular notebooks. In comparing the two tables, you can see that the Moleskine standard paper is thinner than standard copy paper. While I have used Moleskine for several years, I recently transitioned from the standard weight to the art weight. I have been pleased with the thicker pages. I’ve also noticed that the feel of the paper is different. The 165gsm paper seems more absorbent for ink, which is helpful since I am left handed.
It is important to find the right size and thickness of paper for your projects. I wrote this post mostly for myself as a quick reference. Hopefully it will be helpful for you too.