Paper GSM, Points & Coatings: The Print Stock Cheat Sheet

A customer asks for “thick shiny paper for business cards.” Sounds simple. But that one phrase hides at least five decisions - weight, thickness, coating, finish, and which sides are sealed - and getting any of them wrong can turn a premium card into something flimsy and embarrassing.

The good news: the language of print stock is learnable, and once you speak it, print shops treat you completely differently. This guide hands you that vocabulary, the way pros actually use it.

Why this matters

A substrate is just the thing you print on - paper, cardstock, plastic film, vinyl, or board. The word sounds technical, but it only means “the surface the ink lands on.”

Here’s why the details pay off:

• You stop overpaying and under-delivering. Order the wrong weight and your cards feel cheap, or your flyers cost more than they needed to.
• You avoid defects that can’t be fixed. A fold against the grain cracks the coating. A book bound the wrong way warps. These are permanent.
• You earn trust. Walk into a coffee shop and ask for “a hot brown drink” and you get served, but the barista clocks you as a beginner. Say “double-shot flat white, oat milk” and you’re treated as someone who knows the craft. In print, “thick shiny paper” is the hot brown drink. “16pt C2S silk, grain long” is the flat white. Same product, completely different conversation.

There’s one twist that trips up almost everyone, so we’ll tackle it first: two different measuring systems collide in this industry. Most of the world uses metric (GSM, microns). The United States uses an older pound system that confuses even seasoned pros. You need to understand both.

Paper weight: GSM vs the US “lb” system

Paper weight tells you roughly how heavy and substantial a sheet feels. Heavier usually means more premium - though, as you’ll see, heavier and thicker are not the same thing.

GSM - the clean, universal system

GSM stands for grams per square meter. The definition is beautifully simple: take a sheet that’s one meter by one meter, weigh it in grams, and that number is the GSM.

The magic of GSM is that it’s absolute. 90 GSM is 90 GSM no matter the paper type, the manufacturer, or the country. This is why it’s the international standard and the number worth anchoring everything to.

Here are weight anchors worth memorizing - each maps a number to a real-world feel:

GSM	What it feels like
~80 GSM	Standard office copy/printer paper
90–120 GSM	Quality letterhead, nicer text pages
120–170 GSM	Flyer and brochure body paper
200–250 GSM	Light postcard / thin card
300–400 GSM	Business card cardstock
400–600+ GSM	Premium / luxury cards

US “lb” basis weight - and why it confuses everyone

The American system measures weight in pounds (lb), and this is where things get slippery. The basis weight is the weight of 500 sheets (a stack called a ream) - but cut to a special basis size, the large uncut “parent” sheet for that grade. It is not the size you actually buy.

The catch: every grade of paper has a different basis size. So the pound number is measured against a different starting sheet depending on the paper type.

Grade family	Basis size (uncut parent sheet)
Bond / Writing	17 × 22 in
Text / Book / Offset	25 × 38 in
Cover	20 × 26 in
Index	25.5 × 30.5 in
Tag	24 × 36 in

This is the single biggest source of confusion in paper buying. 80 lb Text feels like a sturdy flyer. 80 lb Cover feels like a business card. Same “80 lb,” wildly different sheets - because Text is weighed on a 25×38 parent and Cover on a 20×26 parent. The “lb” number only tells you the weight within one grade family, never across families.

A real-world trap: A customer says, “I want 80 lb paper for my business cards.” If you blindly order 80 lb Text, you’ll deliver something close to flyer paper - flimsy and disappointing. They almost certainly meant 80 lb Cover (~218 GSM). Always ask “Text or Cover?” - or better, talk in GSM and skip the ambiguity entirely.

A quick conversion reference

Because each grade converts differently, you need grade-aware tables. Here are the common ones:

Pounds (lb)	As Text	As Cover	As Bond
16 lb	-	-	60 GSM
20 lb	-	-	75 GSM
24 lb	-	-	90 GSM
60 lb	90 GSM	163 GSM	-
70 lb	105 GSM	189 GSM	-
80 lb	120 GSM	218 GSM	-
100 lb	150 GSM	270 GSM	-

Need a rough mental estimate? Text → Cover ≈ ×0.55; Cover → Text ≈ ×1.80; Bond → Text ≈ ×2.50. And here’s a famous overlap that shows just how slippery pounds are: 50 lb Bond ≈ 80 lb Text ≈ ~120 GSM - three different names for essentially the same sheet.

Thickness (caliper): points, mil, and microns

Caliper is the physical thickness of a sheet, measured with a micrometer (a tool that squeezes the sheet and reads its depth). Caliper measures thickness - not weight.

That distinction matters more than it sounds. Weight (GSM) and thickness (caliper) don’t track perfectly. A fluffy, bulky uncoated sheet can be thicker than a heavier coated sheet of the same GSM, because coatings and a polishing process called calendering compress the fibers. Two stocks both labeled “300 GSM” can feel visibly different in thickness.

The units

Unit	Meaning	Used for
Point (pt)	1/1000 of an inch (0.001”). So 14pt = 0.014”	Cards, postcards, board
Mil	Same as a point - 0.001”	Plastics, films, synthetics
Micron (µm)	1/1000 of a millimeter	International specs

One warning worth tattooing on your brain: the print point (1/1000 inch, thickness) is not the typography point (1/72 inch, font size). They share a name but are unrelated. “14pt cardstock” and “14pt type” mean entirely different things.

The business-card thickness ladder

Business cards are spec’d by points, and this ladder is standard industry vocabulary:

Caliper	~GSM (coated card)	Feel / use
8–10 pt	~200–230	Flimsy, low-end
12 pt	~260	Light
14 pt	~310	The workhorse default
16 pt	~350	Premium-feeling standard
18 pt	~400	Heavy, substantial
32 pt	~0.813mm	Thick luxury (often two sheets glued = duplexed)

The practical rule: spec cards and postcards by pt, and books or flyers by GSM. Track both, because they answer different questions - weight drives shipping cost, while caliper drives how the product feels in the hand.

Coated vs uncoated, and the finish spectrum

Whether paper is coated or uncoated changes everything about how it looks, feels, and behaves with ink.

Coated paper

A thin layer of clay or polymer seals the surface, so ink sits on top of the sheet instead of soaking in. The result: sharper images, denser and more vibrant color (printers call this good ink holdout), and tighter control of dot gain (the tendency of ink dots to spread on contact).

Coated stock is also durable - it resists smudges, fingerprints, and moisture, which is why menus and cards are usually coated. The downside: it’s hard to write on with a pen, because ink and graphite won’t grip a sealed surface (unless it’s a matte coat).

Uncoated paper

No coating. The surface is porous and absorbs ink, giving softer, more muted color and a bit more dot gain. It has a natural, tactile feel, no glare, and you can write on it easily - which is why letterhead, forms, and book pages are usually uncoated.

Uncoated stock also carries an “organic / premium” branding signal. It comes in surface textures: wove (smooth), laid (fine ribbed lines), linen (cloth-like), and felt.

The coated finish spectrum

Finish	Sheen	Strengths	Weaknesses
Gloss	High shine	Punchy color, photo contrast	Glare, hard to read text, shows fingerprints
Silk / Satin	Semi-gloss midpoint	Eye-catching but low glare; great for text + images	Less “pop” than gloss
Matte / Dull	Minimal sheen	Easy reading, elegant, writable	Less vibrant, can scuff

Note that silk and satin mean the same thing, and some shops call matte coated stock “dull.”

C1S vs C2S - the high-trust vocabulary

These abbreviations tell you which sides are coated, and using them correctly signals real fluency:

• C2S = Coated 2 Sides. Both sides sealed. Used for brochures, postcards, catalog pages, and double-sided business cards.
• C1S = Coated 1 Side. One side coated for print quality, the back left uncoated. Used for hang tags, labels, table tents, book and dust covers, and packaging - because the uncoated back accepts glue, writing, or lamination.

The guiding principle: match the finish to how the piece is used. Gloss for photos and marketing; matte for anything text-heavy or written on; silk/satin when you need both readability and a bit of shine. A glossy form people must write on is a guaranteed complaint.

Grain direction: the detail that earns respect

Here’s the concept that quietly separates pros from amateurs. During manufacturing, paper flows through the machine in one direction, and the tiny fibers line up with that flow. That alignment is the grain direction.

• Grain Long (GL): fibers run parallel to the longer edge of the sheet.
• Grain Short (GS): fibers run parallel to the shorter edge.

The labeling convention: grain runs in the direction of the last dimension listed. So 23 × 35 is grain long (grain runs in the 35” direction), while 35 × 23 is grain short.

Why grain matters so much

Think of paper fibers like the grain in a piece of wood - it bends and breaks differently depending on direction.

• Folding and scoring: Always fold parallel to the grain. A parallel fold bends fewer fibers for a clean crease. Folding against the grain snaps fibers and cracks the coating, leaving a visible white line - especially ugly on heavy coated stock, where it looks like a defect. The fix is to score first (press a crease line before folding).
• Binding books: Grain must run parallel to the spine. Then the book lies flat and pages turn easily. Wrong grain gives stiff pages and a warped, wavy spine - a defect called gusseting that’s nearly impossible to fix.
• Press feeding: Grain perpendicular to the feed path keeps the sheet stiff through the rollers, reducing jams and improving registration (color alignment).
• Dimensional stability: Paper expands and contracts across the grain far more than along it as humidity changes. Wrong grain causes curl and misalignment on multi-pass jobs.

Four quick ways to detect grain

1. Tear it: tears straight and clean with the grain; jagged against it.
2. Bend it: less resistance bending parallel to grain; stiffer against.
3. Fold it: folds smoother along the grain.
4. Dampen it: moisten one side and the sheet curls along the grain axis.

The three “white” metrics: brightness, whiteness, opacity

These three numbers all describe how white and clean a paper looks, and they’re constantly confused. They measure genuinely different things.

Metric	What it measures (plain English)	Typical range
Brightness	How much of one specific blue light wavelength (~457nm) the sheet reflects. Higher = colors pop more.	80–100
Whiteness	Reflectance across the full visible spectrum in daylight - the perceived “how white” to the eye.	0–100
Opacity	How well the sheet blocks light - stops you seeing print from the other side.	80–98

The shade or tint is the hue of the white: “true white,” “blue-white” (cool and crisp), or “cream/natural” (warm and easier on the eyes for long reading like books).

Many papers contain Optical Brightening Agents (OBAs) - chemicals that absorb invisible UV light and re-emit it as blue, faking extra brightness. The catch: under different lights the paper can look different (a mismatch called metamerism), and OBAs can yellow over the years.

Watch out for show-through: print double-sided on thin, low-opacity stock and you’ll see ghosting - you can read the back through the front. For anything duplex, and especially book interiors, pick high-opacity paper. Higher GSM and added fillers raise opacity.

Common stocks: a quick grade glossary

“Stock” is just the trade word for “type of paper.” Here are the families you’ll meet constantly:

Stock	What it is & where it’s used
Bond / Writing	Office paper and letterhead. Copy paper = 20 lb bond (~75 GSM). Takes a pen, feeds in laser printers.
Text / Book / Offset	Lighter sheets for interior pages, flyers, brochures. 60–100 lb text (90–150 GSM).
Cover / Cardstock	Thick and rigid - business cards, postcards, folders, covers. 65–130 lb cover.
Index	Stiff, smooth, stable - index cards, file dividers, tabs.
Tag	Strong and durable - tags and tickets.
Bristol	Mid-weight smooth board - postcards, drawing.
Recycled	Contains post-consumer waste (PCW). Slightly lower brightness.
Kraft	Brown, unbleached pulp. Strong, rustic look - bags, tags, eco packaging.
Synthetic “paper”	Plastic-film stock (polypropylene, Teslin, Yupo, vinyl). Waterproof, tear-proof. Measured in mil.

One trap with synthetics: don’t send a plastic stock through with ordinary ink. Plastic doesn’t absorb conventional ink, so it won’t dry or adhere - you’ll get smearing. Synthetics need UV-cured or latex ink, or special handling.

Packaging board - a separate world

Paperboard is solid, single-layer board used for folding cartons (the retail boxes products come in). It’s spec’d in points, like cards.

Board type	Description & use
SBS (Solid Bleached Sulfate)	Premium, clay-coated, bright white. Food and high-end retail; best print quality.
CRB / CCNB (Coated Recycled Board)	Recycled blend with a gray interior; the cheapest folding cartons.
CUK / SUS (Coated Unbleached Kraft)	Strong, brown, moisture-tolerant - beverage carriers, rugged packaging.

Corrugated fiberboard is different again: a wavy fluted layer sandwiched between two flat liners - this is for shipping boxes, not folding cartons. It’s spec’d by flute size (A/B/C/E/F) and strength tests, not GSM.

Wide-format and banner substrates

Banners are roll-fed and weighed in ounces per square yard or GSM:

• Scrim vinyl banner: the standard. 13 oz (~400–500 GSM) for most uses; 18 oz (~550+ GSM) for heavy-duty outdoor.
• Mesh vinyl: perforated so wind passes through (fences, building wraps). ~250–350 GSM.
• Fabric / polyester banner: 150–300 GSM; elegant, low-glare - trade shows, retractable displays.

The rule of thumb: higher GSM or oz means sturdier and more wind/UV resistant.

Common misconceptions

• “Heavier paper is always thicker.” Not true. Coatings and calendering compress fibers, so a heavy coated 300 GSM sheet can be thinner than a bulky uncoated 300 GSM sheet. Weight and thickness are separate measurements.
• “80 lb means the same thing everywhere.” It doesn’t. 80 lb Text and 80 lb Cover are wildly different because they’re weighed on different parent sheets.
• “A point is a point.” The print point (thickness) and the typography point (font size) are unrelated despite the shared name.
• “Brighter paper is whiter paper.” Brightness measures one blue wavelength; whiteness measures the full spectrum. A high-brightness sheet can still look cool or warm depending on its shade.
• “Any ink works on any stock.” Synthetic and plastic stocks reject conventional ink and smear. They need UV or latex ink.

How to use this: choosing the right substrate

Put it all together with these practical defaults.

1. Business cards: Cover/cardstock, 14pt or 16pt (~310–350 GSM), C2S silk or matte. Gloss for photo-heavy designs; uncoated or cotton for a premium tactile feel; 32pt duplex for luxury.
2. Flyers / leaflets: Text weight ~100 lb text / ~150 GSM. Gloss for vibrant single-use marketing; matte if text-heavy or written on.
3. Postcards: Cover stock, 14pt. Watch USPS caliper minimums for mailing (~0.007” minimum, 0.009”+ for the postcard rate) - too thin and it gets rejected, surprising your customer with extra cost.
4. Brochures (folded): Text weight that folds cleanly. Fold parallel to grain, and score heavy coated stock to avoid cracking.
5. Booklets / books: Body 70–100 lb text (90–150 GSM) with high opacity; cover 80–100 lb cover or C1S; grain parallel to the spine.
6. Posters: Gloss or satin photo paper; heavier for durability.
7. Banners: 13 oz scrim vinyl by default; mesh if windy or outdoor; fabric for indoor premium.
8. Packaging boxes: SBS for premium and food; kraft for eco and rugged; CRB for budget; corrugated for shipping.

And a habit that earns instant trust: quote every stock in one complete shape. For example, “350 GSM (16pt) cover, C2S silk, grain long.” That single string answers weight, thickness, grade, coating, sides, and grain - everything a print shop needs to do the job right.

Conclusion

If you remember one thing, make it this: anchor everything to GSM, keep weight and thickness as separate facts, and never forget grain on anything that folds. Those three habits prevent the most expensive and embarrassing mistakes in print.

Master this vocabulary and a strange thing happens - print shops stop treating you like a beginner and start treating you like a peer. The conversation shifts from “what do you mean by thick?” to “great, let’s run it.”

And here’s the next rabbit hole: once you’ve chosen the perfect stock, how does the ink actually land on it? The answer lives in color - CMYK, spot inks, and why the blue on your screen never quite matches the blue on the page. That’s where the real magic (and the next round of gotchas) begins.