Inkjet Paper Physical Specs – A Primer on Weight and Thickness

Posted on May 1, 2012 | 1 comment

Here are the different ways to physically quantify photo inkjet papers.  Keeping these numbers and scales in mind will help you visualize an inkjet paper based on its specs, either online or on a store shelf.

Weight

Weight is the measure of density of paper, or how heavy it feels.   There are two popular units of weight you will see:

Pound Weight – There are actually many different pound weight scales used in the paper industry.  The popular one for inkjet paper is the Bond Basis.  If you can imagine a 20lb. sheet of copy paper, then you have a reference for the Bond Basis.  (Paper Nerd Note: We get the Bond Weight of a paper by physically weighing 500 sheets of 17″ x 22″)

Grams per Square Meter or GSM – This scale is used extensively inside our industry and outside of North America.  It is the weight in grams of square meter sheet of paper.

Thickness

Thickness is measured in mil, or thousandths of an inch.  In many cases, knowing the thickness of a paper is more important to gauging printer compatibility than other specs.  Keep in mind that thickness is related loosely to weight, but the two specs are not completely linked.

5mil = Copy paper
8mil = Photo book and quality brochure paper
10.4mil = Photo lab type paper
15+ mil = Cotton fine art and specialty media

Other Specs

There are other specs like stiffness, brightness, and opacity. These are technical numbers and all can be reported using different scales (ISO vs. ASTM).  These specs are problematic when it comes to using them in making a buying decision.  While the machine measuring them can certainly discern small differences, the human eye and touch are not really capable of quickly picking up on differences. For example, a 94 vs. 98 brightness paper will look quite similar depending on your lighting conditions.  So as a rule we do not recommend relying on them too heavily.