When 30 Equals 33: America's Bizarre Methods of Calculating the Weight of Paper

My fellow Americans mostly seem allergic to anything having to do with the metric system. Can’t remember how many teaspoons go into a tablespoon? Is our country falling behind in science because we’re handicapping our kids with the “English” measurement system. Doesn’t matter.

 “WAM: We ain’t metric!” my countrymen kneejerk. After all, if you give those socialist, one-world-government Europeans 2.54 centimeters, they’ll take 1.60934 meters.

But when it comes to specifying the weight of paper, even some red-blooded Americans throw up their hands and say “What’s that in GSM?”

There’s never been a better time for U.S. buyers of graphic paper to understand what GSM (grams per square meter) means – and how messed up our own system of basis weights is.

Publishing Executive just published a piece I wrote noting that U.S. prices for magazine-quality paper are at record high levels in comparison with European prices. That means it’s a great time to look overseas for paper, especially since North American mills are gearing up to raise prices again in July. But to get the best deals, you might need to understand how the rest of the world talks about paper weight.

I’m reminded of a colleague’s story about buying 33# SCB paper (lower quality than coated paper but better than newsprint) from a non-U.S. mill. When the shipment arrived at a U.S. printing plant, the printer notified my colleague of an error: The rolls were marked “30#” (pronounced “30 pound”), indicating the paper was about 9% lighter and thinner than intended.

The mill’s sales office had correctly translated the order from 33# to the more universally understood 48.9 gsm. But the mill was only used to making newsprint for U.S. customers, so it thought 48.9 gsm translated to 30# in Americanese. The paper was OK; the label was just wrong.

From Catalyst Paper's "How We Make Paper"

A page of 30# newsprint, you see, weighs the same as a 33# page of magazine-quality paper (and of other publication grades that use the “book, text, offset” method of calculating basis weight).But two same-sized sheets of 48.9 gsm always weigh the same, regardless of whether one is copy paper and the other wallpaper or tissue or newsprint.

The U.S. has 11 different systems for calculating the basis weight of paper. Standard resume paper is 20# bond – generally a nice stiff, opaque sheet. It’s also more than 2½ times the weight of 20# coated paper, which is an extremely thin, translucent paper that is likely to be used in dictionaries or Bibles.

Confused? Wait, it gets worse. When magazine publishers refer to 80# cover stock, they usually mean something that, logically enough, is double the weight of the 40# coated paper they might use on their internal pages. The rest of the world would say the publisher is using 59 gsm text stock and 118 gsm cover stock.

But “80# cover” can also refer to paper that is measured based on the “cover” method of calculating basis weight rather than the “book, text, offset” method. It weighs 216 gsm. Thus, even when Americans are speaking to Americans, a request to use 80# cover stock can easily result in the pressroom printing covers that are too heavy for the saddle stitchers that are supposed to bind the publication and too expensive for the publisher's budget.

Many overseas mills are accustomed to making paper for U.S. customers, knowing, for example, that 40# coated paper should be 59.26 gsm. And if they make a lot of paper for U.S. customers on a steady basis, they might actually make a “true 40#” that is indeed targeted at 59.26 gsm.

But rather than manufacturing a special batch of paper for the U.S. market, many mills will just make 60 gsm, which is a common weight for European magazine papers that comes out to 40.5# in Americanese. That results in using more paper and having higher postage and freight costs versus true 40#. But it’s not a reason to avoid overseas paper.

For my fellow American buyers of magazine grades like coated and supercalendered papers, as well as for book papers, here’s the key formula: 0.675 gsm is equivalent to 1# of basis weight. European mills typically offer weights that are about 1.3% above the U.S. equivalents – e.g. 45 gsm (30.38#) in place of 30#, 51 gsm (34.43#) in place of 34#, or 60 gsm in place of 40#.

A good rule of thumb is that such weight differences will cost publishers about 2%, a bit more if the copies are mostly mailed, a bit less if many are sent via the newsstand system. So if I’m buying 40# coated #5 paper for 40 cents per pound, I might consider a price of 39.20 cents for 60 gsm to be competitive, but not a bargain.

And since that 60 gsm was recently selling for something like 33 cents in Europe, I know the manufacturer has plenty of incentive to be more than just competitive in the U.S. market.

A footnote about Canadian paper: Canadians have pretty much converted to the metric system, but their mills sell so much paper into the U.S. that they usually spec it to U.S. standards and practices. Thus, Canadian paper is pretty much like U.S. paper except that it occasionally throws in a random “Eh?” at the end of a sentence.