Understanding paper weight is a mysterious  challenge created by three measuring systems.

• North American Standard In Pounds
• Metric system in Grams Per Square Meter
• Caliper in Points

In North America, we most comonly see a confusing system of imperial measures developed 100 years ago combined with equally antique U.S. Government purchasing standards to identify paper stocks. Endless charts and calculators are available to crack the code to a North American system run amok while the rest of the world uses a much simpler system.

North American Standards

Bear with me, we can unravel the mystery. Our system begins with a standard loosely described as "the most popular historical use" of a given paper type such as bond, text, cover, and so forth. There are many more but we'll keep it simple. Each of these paper types begin the calculation with its very own "basic size" often called a "parent sheet",  and the weight of 500 parent sheets in pounds is the "Basis Weight" you see on the retail shelf regardless of the final cut size. The chart below shows a brief sampling of common paper types and the basic size.

From this example, we see that 500 parent sheets of Bond or Writing paper has a basic size of 17x22 inches which will be cut and packaged into standard cut sheet sizes of 8½x11 or 11x17 sheets. We can further conclude that if the same five hundred 17x22 sheets of a  writing stock weighs 24 pounds, it will be identified as 24# stock. Seems simple enough if you always work from the paper type and the basic size, but not many outside the industry think this way.

But wait! There's more to understanding paper weight!

Is 100# Cover the same as 100# Text? Will your standard 80# Cover business card be heavier and stiffer with 90# Index stock? Actually, the answer is no because your comparison does not use the same size basic sheet. There is no joy in this exercise but there are solutions.

The solution is three-fold. You can visit local print professional to see actual samples, you can use the paper manufacturers conversion tools on their web sites, or you can use a reference chart such as the brief sample we included to compare approximate equivalent weights.

Metric Standards

Metric paper weights are simply the weight of a single sheet expressed in Grams Per Square Meter (GSM). That is the entire formula. It works for every stock regardless of paper type and the old concept of "Basic Size" is fixed at one square meter. This measurement system is quickly becoming more widespread in North America with the adoption of digital print devices and foreign paper stock imports. It is now common to see the paper weight in GSM reference along with the traditional weight on retail cut sheet packaging.

Caliper

Caliper is the thickness of a paper sheet expressed in thousandths of an inch translated to Points. There is no consideration for sheet size, paper type, or weight. It is that simple. You most often see Caliper used to reference cover stocks, particularly coated stocks such as 10 Point, 12 Point, and so forth.

Here we see several weights presented by the manufacturer on the package label. This is a 28# Writing stock typically used for letterhead. The weight is 70# Text, 28# Writing, and 104 GSM. All of these weights refer to this package of paper. So, which is heavier?

The best solution is always consult with your local print professional if you have any doubt. Working daily with paper weights as part of the print process, we are always happy to answer your questions.