In Printing – Why are paper weights so confusing?

Why are paper weights so confusing?

For example you may have read or head that 20lb “bond” is the same as 50 lb “offset”. That is in fact true!

Somehow back in the old days, paper mills decided that they would weigh 500 sheets of a given size, called the basis size (not “basic”). So in their infinite wisdom they decided that the “bond” basis size would be 17” x 22”. In other words, in the “bond” classification the weight of 500 sheets of 17” x 22” was 20lbs. Therefore it would be called “20 lb bond”. Now it’s important to note here that within the bond classification there are several other sub classifications such as “Ledger”, “Mimeo”, “Duplicator” and  “Rag Paper”. These four additional sub classifications all share the same “basis size” ie 17” x 22”. So 500 sheets of “20 lb.) “Duplicator” paper will also weigh exactly 20 lbs.

So, now back to the first paragraph above. The mills also made several other classifications of paper. The next one we’ll discuss is “Offset”. Again, within the “Offset” classification we find several other sub-classifications such as “Book” “Text” and “Coated Paper”. Now, once again in their infinite wisdom, what do they do? They choose a different basis size of 25” x 38”. So they weigh 500 sheets of 25” x 38” Offset and it weighs “50 lbs”. So that’s why it’s called “50 lb”. Now you see why it’s pretty darn confusing for the layman to wrap his mind around this stuff.

We’ll also briefly mention that it doesn’t end there, example; for “Cover” the basis size is 20″ x 26″ and for “Tag Stock” the basis size is 24″ x 36″ and for “Index” it’s 25 1/2″ x 30 1/2″.

In the past 10 or 15 years there’s been an effort to eliminate as much confusion as possible, many paper mills have now chosen GSM as their conversion reference point, because it is a definite and universal measure of the paper. GSM stands for grams per square meter, which is the actual weight of the sheet.

In order to clarify this we have provided a handy chart reference. This will show probably all you’ll need to know when ordering printing or specifying paper for a print job. We’ve provided this in pdf format so you can easily print it.

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