When manufacturers produce paper, they weigh it 500 sheets at a time, and that number in pounds is documented as the weight of the paper. So does that mean that a ream (500 sheets) of 8.5” x 11” 20 lb. plain Bond paper weighs 20 pounds? It does say “20 lb.” right here the label after all. Nope. A ream of this plain Bond paper actually weighs 5 pounds. Confusing, right? So why do we call it “20 lb.” paper if it weighs 5 pounds?  When the manufacturer weighs the paper it’s not 500 8.5” x 11” size sheets, it’s 500 17” x 22” size sheets which are 4x the size of 8.5”x11”. Some quick math and that works out to a weight of 5 pounds for a ream of 8.5” x 11” size paper. Bingo, problem solved! But wait…that would just make it too easy. The example above is for Bond paper, which is the common everyday paper you’re used to printing on. Moreover, this is thin paper so it’s not likely going to be the culprit of your paper jam.  When we run into feeding and jamming issues it’s usually with heavier weights, commonly called Index, Cover or Bristol stock. Now consider this: 20 lb. Bond = 41 lb. Index. What?! Paper weight changes based on the TYPE paper it is.  This is because Index does not use 17” x 22” sheets when weighing the paper. Index is manufactured in 22.5” x 30.5” sheets. (To confuse matters more, Cover stock uses 20” x 26” sheet size and Bristol uses 22.5” x 28.5” sheet size for weight measurement.) Oy. So what does this all mean, other than confusing the heck out of everyone? The bad news is that we can’t just look at how many pounds the paper weighs in order to figure out if it’s too heavy for the machine. The good news is that there’s a measurement that takes paper type/pounds out of the equation. On most ream labels, you will find a specification called GSM. This stands for grams per square meter, and is a measurement of the paper's density. The higher the number, the thicker the paper. Not only is this almost always listed, but it’s the measurement most printers and copiers will ask for when you set a new paper type up for a tray. So how heavy it too heavy then? If the GSM weight isn’t an option in the printer’s paper settings, it’s probably too heavy. Xerox also lists the GSM specifications in their device documentation so if you reference that, you will know if your paper is within the working range of your machine. Final thoughts… Whenever you are loading a new paper type, take a look at the label on ream to find the GSM then compare that to what your machine is capable of handling. from https://www.lewan.com/blog/understanding-paper-weight-for-printing-how-is-it-calculated-and-why-does-it-matter

here is a quick guide we created to help you determine the best paper weight for your projects. 20 lb. paper / 75 gsm This is the standard weight of most copy paper, and the thinnest/lightest weight we offer. It’s perfect for everyday printing and copying on laser and inkjet printers for projects at home, school, or in the office. Because it is so thin, you may find it a bit too flimsy for things like wedding programs, brochures, or similar projects where you would want to make a statement with a heavier stock. However, it works perfectly for simple flyers or posters, and folds easily into a variety of craft projects such as origami. 24 lb. paper / 89 gsm This multipurpose paper is just a bit heavier than copy paper stock, and works for all the same applications. The color options we offer in this weight make it especially great for crafting bold and vibrant works of art. This paper also folds easily and can be used for origami projects, or it can be cut into strips and used to create intricate paper quilling designs. 28 lb. paper / 105 gsm This paper is slightly thicker than 24 lb., making it popular for business letterhead, resumes, stationery, newsletters, and other professional pieces that require something a bit more substantial.  67 lb. vellum / 147 gsm Our standard cardstock can be considered a lightweight cardstock. It’s noticeably thicker than paper, but it’s not the heaviest of cardstocks. It runs smoothly through inkjet and laser printers, and can be used to create printed pieces such as invitations, posters, business cards, and more. We recommend lightly scoring the cardstock to create crisp folds if you want to make crafts such as boxes or folded greeting cards. The thickness of this cardstock makes it ideal for detailed cut shapes and designs created with desktop cutting machines or paper punches. 65 lb. cover / 176 gsm This weight is slightly heavier, but very similar to the 67 lb vellum. It works great for layered greeting cards or scrapbook pages, because it is another lightweight cardstock that is sturdy but won’t add too much extra thickness to the piece. We also offer a variety of colors to use in such layering projects, or to create vibrant decorations for classrooms or parties. It folds, prints, punches, and cuts easily for all sorts of crafting needs. 110 lb. index / 199 gsm This cardstock weight is typically used for index cards due to its sturdiness. It is more noticeably thicker, but can still be used for applications such as cutting, printing, and folding. This premium cardstock is great for when you want to make a statement with DIY event pieces such as programs, invitations, RSVP cards, menus, and more. It is also ideal for photo and frame mats, gift tags, pop up cards, and tons of other projects. 80 lb. cover / 216 gsm This stock is perfect for heavier applications, and again, for any project where you want to make a statement, such as professional-looking business cards. It’s also an ideal weight for embossing, as well as cutting intricate designs with cutting machines. As with other cardstocks, but especially because this is much thicker, we suggest scoring the paper for a clean fold. from https://pariscorp.com/paper-weight-guide/