I'm going to temporarily stray from the Do's and Don'ts that I've been writing lately to address a subject that we get a lot of questions about: paper weights.
Paper weights can be a bit confusing. I mean, how is it that a 65 lb. cover stock is heavier than a 90 lb. index paper? Give me a few minutes of your time and hopefully it will be a little clearer.
There are two basic systems used to measure paper - the pounds system used in the U.S. and the GSM (grams per square meter) system used everywhere else.
Let's take a quick minute to discuss the different kinds of paper before moving on. Paper is divided into basically two categories - text weight and cover weight. In the U.S., "text weight" papers, also called book, bond or offset, normally range from 20-100 lb. These are the types of papers that you would use for letterhead, flyers, brochures and the like. "Cover stock" is many times used interchangeably with the term "card stock" and there are several different sub-categories of this stock, such as bristol, tag and index. They generally range from 60-140 lb. These are the thicker papers that you would use for invitations, tabs, post cards, etc. So you can already see by my descriptions that you can have an 80 lb. text/offset weight paper and an 80 lb. cover stock. But......those two 80# papers don't weigh the same.
Why, you ask?
Stay with me now - here's the important stuff.
In the U.S. system, paper weights don't really refer to the weight of the sheet of paper you have in your hand. The whole "weight" thing is deceiving because the weight marking on the ream of paper you buy is based on the weight of 500 sheets of that paper in its full (or "basis") size - not 500 sheets in the cut size that you bought. Different kinds of paper have different thicknesses and basis sheet sizes vary by the type of paper, so that accounts for the funky weights. Here's a quick comparison of the basis sheets:
Basis Sheet Sizes
Bond - 17" x 22"
Offset -25" x 38"
Cover - 20" x 26"
Tag Stock - 24" x 36"
Index - 25-1/2" x 30-1/2"
500 sheets of 80# cover weighs more than 500 sheets of 80# offset. The basis sheet sizes are different and, although the basis sheet size of the 80# offset is larger (25" x 38") than the basis sheet size of the 80# cover (20" x 26"), 80# cover is a thicker, sturdier paper, so 500 sheets, even in a smaller basis sheet, is heavier.
Here's a chart that illustrates everything I've just said. The U. S. system is on the top and the GSM markings are underneath (except the 64 lb tag and the 100 lb tag are U.S.).
I know some of you are still shaking your heads. And what about the GSM markings that I see on papers I buy, you ask? Every other place in the world measures paper in GSM (grams per square meter) - the weight in grams of a 1 meter by 1 meter sheet of that paper stock. (The U.S. is the only country that uses the pound system.) If a 1 meter by 1 meter sheet weighs 120 grams, that paper is marked 120 gsm. Much simpler, right? And the fact that papers are sold here in the U.S. with the GSM markings on them confuses people because they're not familiar with it and don't understand it. Looking at the chart above, you can see that the GSM system is much more straightforward and easy to understand.
I've always vehemently refused to learn the metric system because I live in the United States and we use pounds here, but even I have to admit that this is one instance where metric is better.
I hope this has helped to clear things up a bit for you. If you need advice on the type of paper to use for your next project, give us a call - we're happy to help!