Paper Weight Guide: GSM, Pounds, and Choosing Stock

Paper weight trips up more print buyers than any other spec, and for one maddening reason: the same number can mean two completely different sheets. “80 lb” text folds into a brochure. “80 lb” cover is stiff enough for a business card. Both say 80. This guide explains why, and how to pick the right stock the first time.

Here is the short answer. Paper weight, properly called basis weight, is the weight in pounds of 500 sheets of a paper cut to a standard “basic size” for its grade, as Neenah Paper defines it. Because bond, text, and cover papers each use a different basic size, the pound numbers only compare within the same grade. GSM (grams per square metre) fixes the confusion by measuring every paper the same way.

Key Takeaways

• Basis weight is the weight of 500 sheets at a grade’s basic size, so pound numbers only compare inside the same grade (bond, text, or cover).
• GSM measures every paper as grams per square metre, which makes it the reliable cross-grade number.
• Weight and thickness are separate specs. Caliper, measured in points at 0.001 inch each, tells you stiffness. Weight alone does not.
• For mailed postcards, USPS sets the floor: card-price pieces must be 0.007 to 0.016 inch thick.
• Match the weight to the job. Cover stock for cards and postcards, text stock for letterhead and brochure interiors, paperboard for folding cartons.

What paper weight actually measures

Basis weight is the weight, in pounds, of a ream (500 sheets) of paper cut to the basic size for its grade, according to Neenah Paper. That last part is the whole trick. The “basic size” is not the size you buy. It is a reference sheet the industry agreed on decades ago, and it is different for each grade.

Three basic sizes cover most commercial printing. Bond (the family that includes copy and writing paper) is measured at 17 by 22 inches. Text and book papers are measured at 25 by 38 inches. Cover stock is measured at 20 by 26 inches. So “20 lb bond” means 500 sheets of that big 17 by 22 parent sheet weigh 20 pounds. It has nothing to do with the 8.5 by 11 sheet in your printer.

This is why the pound number lies to you across grades. A text sheet and a cover sheet start from different reference dimensions, so their weights were never on the same scale to begin with. Compare weights inside one grade and the number is honest. Jump between grades and it stops meaning anything.

Pounds versus GSM, and why 80 does not equal 80

GSM is grams per square metre, and it is defined by a single international standard: ISO 536 specifies how to determine the grammage of paper and board, expressed in grams per square metre. One square metre of the sheet, weighed in grams. That is it. No reference sizes, no grade tables, no math you have to trust.

Because GSM measures area the same way for every paper, it exposes what the pound system hides. Here is the proof, using published conversions from Neenah Paper: 80 lb text is 118 g/m², while 80 lb cover is 216 g/m². Same “80,” nearly double the mass. The cover sheet is not a little heavier. It is a different animal.

If you only remember one habit from this guide, make it this: when someone quotes a weight, ask which grade, or ask for the GSM. Those two numbers together remove all the guesswork.

Weight is not the same as thickness

Weight and thickness are two different measurements, and assuming one from the other is a common, expensive mistake. Thickness, called caliper, is measured in points, where one point equals 0.001 inch, and Case Paper notes that two sheets of the same basis weight can measure different thicknesses. A rougher, bulkier sheet stands taller than a smooth one at the identical weight.

That gap matters whenever stiffness or feel is the point. A 14 pt card and a 12 pt card can weigh nearly the same on paper, yet the 14 pt version snaps in the hand while the 12 pt one flexes. Packaging engineers care about caliper for exactly this reason, because a folding carton has to hold its shape on a shelf, not just hit a target weight.

So read both numbers. Weight tells you about mailing cost and how the sheet behaves on press. Caliper tells you how rigid and substantial the finished piece feels. A quote that lists both is a quote you can actually judge.

How to choose paper weight by project

Start from the job, not the number, because the right weight is the one that survives how the piece gets used. Using the Neenah conversions above as anchors, here is how the common projects tend to shake out.

• Business cards and rack cards. Cover stock, commonly 100 lb cover (270 g/m²) and up. It needs to feel like a card, not a coupon.
• Letterhead and stationery. Text or writing weights around 70 to 80 g/m² so the sheet runs cleanly through office printers and takes a fold. Matching custom envelopes finishes the set.
• Brochures and booklet interiors. 80 lb to 100 lb text (118 to 148 g/m²) for the inside pages, then a heavier cover wrapped around it. The bindery and finishing step is where those pieces get folded, scored, and bound.
• Postcards and mailers. Cover stock heavy enough to clear postal minimums (more on that next). This is the backbone of most direct mail and Every Door Direct Mail campaigns.
• Folding cartons and packaging. Paperboard chosen by caliper, not office-paper weight, so the box holds its structure. That is a custom packaging conversation from the start.

When a project mixes weights, like a booklet with a thick cover and thinner insides, spec each component separately. One weight almost never fits an entire piece.

Paper weight for direct mail and postcards

For anything you mail, the post office sets the floor, so start there. To qualify for the First-Class Mail postcard price, USPS requires a card to be at least 3.5 by 5 inches and 0.007 inch thick, and no larger than 4.25 by 6 inches or thicker than 0.016 inch. Thin stock is not just flimsy. It can be rejected or chewed up in automated sorting.

Translate that into stock and it gets easy. Since one point equals 0.001 inch, the 0.007 inch minimum is 7 pt, and a common 14 pt cover clears it with room to spare while still feeling substantial in the mailbox. Go too light to save a few dollars and you risk the whole drop, which is a false economy on a campaign you already paid to design and mail.

Weight also interacts with what you print. Heavier cover stock holds saturated color and full-bleed images without curling, which is why it pairs well with variable data printing runs where every piece carries a different name, offer, or image. Get the stock right and the personalization lands on a card that feels worth reading.

Does the press change what weight you can run?

The process you print on shapes both cost and stock range, so it belongs in the weight conversation. On lithographic offset printing, making plates and bringing the press up to color is a real fixed setup cost, and once it is paid the cost per piece drops sharply, which is why offset wins on long runs and holds color consistently across them. Digital printing skips the plates, so it is the smarter call for short runs and fast turnarounds.

Both processes handle a wide range of stocks, from light text weights up through cover. Very heavy paperboard for boxes and cartons is a different lane again, run on packaging equipment built to score and die cut thick board without cracking it. The practical move is simple: bring the finished piece and how it will be used, and let prepress match the weight, the stock, and the press together. Ka-Pow, one decision instead of three.

Frequently Asked Questions

Is GSM or pounds better for specifying paper?
GSM is the more reliable number because it measures every paper the same way, as grams per square metre under ISO 536. Pounds work fine inside a single grade, but they are only comparable within that grade, so pairing a pound value with either the grade or the GSM removes the ambiguity.

Why does 80 lb text feel so much thinner than 80 lb cover?
Because the two grades are weighed at different basic sizes, the pound numbers were never on the same scale. In GSM terms the difference is plain: 80 lb text is about 118 g/m² and 80 lb cover is about 216 g/m², per Neenah Paper.

Does a higher weight always mean a thicker sheet?
No. Weight and thickness are separate specs, and Case Paper notes that two sheets of the same basis weight can differ in caliper depending on finish and bulk. Check the caliper in points when stiffness or feel is what matters.

What paper weight do I need for a mailed postcard?
Enough to meet the postal minimum. USPS requires postcard-price pieces to be 0.007 to 0.016 inch thick, and a common 14 pt cover stock clears that comfortably while surviving automated handling.

What weight should business cards be?
Most business cards use cover stock, commonly 100 lb cover (about 270 g/m²) or heavier, so the card feels solid rather than floppy. If you want extra rigidity, ask about the caliper in points rather than only the pound weight.

Get the right stock, the first time

Paper weight stops being confusing the moment you ask two questions: which grade, and what caliper. Get those on the quote and every other decision, from mailing cost to how the finished piece feels, falls into place. BANG, no more surprises at delivery.

Not sure which stock fits your project? Request a quote and tell us how the piece will be used, or upload your file and we will spec the weight for you. Prefer to talk it through? Call MPress at (504) 524-8248.