GSM vs PT: Comparing Paper Weight and Thickness for Packaging

By Elias DengAugust 20, 2026

GSM and PT often appear together when you compare paper and paperboard specifications, but they do not describe the same thing. GSM measures paper weight, while PT measures thickness. If you treat them as direct equivalents, you can easily misjudge board stiffness, folding behavior, or the final feel of a packaging box.

Table of Contents

This guide compares GSM vs PT for packaging paper and paperboard. You will learn what each unit means, how conversion works, why thickness varies, and how these measurements affect packaging specifications and performance.

What Is Grams Per Square Meter (GSM)?

GSM, or grams per square meter, measures the weight of paper or paperboard based on one square meter of material. For example, a 300 gsm paperboard weighs 300 grams per square meter. GSM is widely used internationally to specify paper weight, especially across Europe, Asia, Australia, and many global packaging supply chains. In North America, you may also see paper specified by pounds (lb), which uses a different basis-weight system.

You will commonly see this measurement used for printing paper, wrapping paper, cardstock, and many paperboard grades. Lighter papers may fall around 80–150 gsm, while heavier cardstock and folding carton boards often range from about 200–400 gsm or more, depending on the material and intended use.

GSM matters because it provides a consistent way to compare the amount of paper used per unit area. It can help you narrow down suitable paper grades, estimate material usage, and communicate specifications with suppliers. However, GSM measures weight rather than thickness, so you still need additional specifications when physical caliper or structural performance matters.

What Is the Point System (PT)?

PT, or point, measures the physical thickness of paper, cardstock, or paperboard. One point equals 0.001 inch, so a 16 pt sheet is 0.016 inch thick, or about 0.406 mm. Unlike GSM, PT describes caliper rather than material weight. The point system is commonly used in North American printing and packaging specifications, especially for cardstock and paperboard.

You may see materials listed as 12 pt, 16 pt, 18 pt, or 24 pt, depending on the board grade and application. Because PT measures thickness directly, it gives you a clearer indication of sheet caliper than GSM alone. However, PT tells you thickness only; it does not tell you the sheet’s grammage.

GSM vs PT: What Is the Difference?

GSM and PT describe two different paper properties: GSM measures weight per unit area, while PT measures physical thickness. A higher GSM generally means more paper mass, but it does not indicate exact caliper. PT, on the other hand, shows how thick the sheet is without telling you its weight. For packaging specifications, GSM is useful for comparing grammage, while PT provides a direct reference for paperboard thickness.

Comparison	GSM	PT
Full term	Grams per square meter	Point
Measures	Weight per unit area	Physical thickness
Unit	g/m²	0.001 inch
Example	300 gsm = 300 g/m²	16 pt = 0.016 inch
Main purpose	Compare paper grammage	Compare paper caliper
Common use	Paper, cardstock, paperboard	Cardstock and paperboard
Indicates grammage	Yes	No
Shows physical thickness	No	Yes
Directly interchangeable	No	No

Can You Convert GSM to PT?

Yes, you can convert GSM to an approximate PT value, but the result is not universal because the relationship depends on the specific paper stock. For practical use, a reference chart can show common GSM and PT combinations for known paper and paperboard types. These values help with initial comparison, while the final caliper should still come from the actual material specification.

Paper Stock	PT	GSM	Thickness	Packaging Relevance
C1S coated stock	10 pt	230 gsm	0.010 in	Sleeves, light cartons, printed wraps
C1S coated stock	15 pt	345 gsm	0.015 in	Folding cartons, tags, premium printed packaging
C2S coated stock	16 pt	406 gsm	0.016 in	Folding cartons and printed paperboard
Textured matte stock	16 pt	350 gsm	0.016 in	Premium packaging, sleeves, presentation pieces
C2S coated stock	18 pt	457 gsm	0.018 in	Heavier folding cartons and premium packaging
Brown kraft stock	15 pt	340 gsm	0.015 in	Kraft cartons, tags, natural-look packaging
Brown kraft stock	18 pt	400 gsm	0.018 in	Heavier kraft packaging
Cotton stock	20 pt	297 gsm	0.020 in	Premium inserts, cards, specialty packaging
Mohawk Superfine	18 pt	406 gsm	0.018 in	Premium printed packaging
Mohawk Superfine	24 pt	433 gsm	0.024 in	Thick premium packaging components

Why Can the Same GSM Paper Have Different Thicknesses?

The same GSM can produce different thicknesses because GSM only fixes the mass per square meter, not how that mass is distributed through the sheet. If the paper structure contains more internal volume, the sheet becomes thicker. If the same mass is compressed more tightly, the sheet becomes thinner. Fiber structure, coating, and paperboard construction are the main reasons this happens.

Paper Density and Fiber Structure

At the same GSM, paper density determines how tightly the material is packed within the sheet. Lower-density board contains more volume per unit mass, so it develops a higher caliper. By contrast, denser board packs the same mass into less space and stays thinner.

Fiber structure also changes the final thickness. Different pulp and paper fiber properties, including fiber length, bonding behavior, and fiber morphology, can create either a more open or a more compact internal structure. More open fiber structures leave additional space between fibers and increase bulk, while compact structures reduce that internal space and lower caliper.

For example, two 350 gsm paperboards can have different thicknesses if one uses a bulkier fiber structure and the other uses a denser, more compact structure. The weight per square meter stays the same, but the internal structure changes the final thickness.

Coated vs Uncoated Paper

Coated and uncoated papers can have the same GSM but different material structures. In coated paper, part of the total grammage comes from the surface coating, while uncoated paper contains a larger share of fiber through the sheet body. Since the fiber body creates most of the sheet’s bulk, uncoated paper can sometimes be thicker than coated paper at the same GSM.

The final caliper also depends on coating weight and surface finishing. A heavier coating can increase GSM without adding much thickness, while processes such as calendering compress and smooth the sheet surface, which can reduce caliper further. So coated and uncoated papers with the same GSM may still have different thicknesses because they build that grammage in different ways.

Paperboard Composition and Manufacturing

Many packaging paperboards use several plies rather than one uniform layer. One board may use a thicker, high-bulk middle ply with thinner surface plies, while another may use a more compact layer structure. Even when both boards have the same total grammage, those different ply combinations can produce different calipers.

Manufacturing then changes the final thickness further. Pressing and calendaring compress the plies to different degrees, while drying affects the final sheet structure. For example, two 350 gsm folding carton boards can finish at different thicknesses if one uses a bulkier ply structure or receives less compression during production. This is why two paperboards with the same GSM can still have different PT values even when both meet the same weight specification.

What GSM and PT Mean for Packaging Performance?

GSM and PT affect packaging performance in different ways because weight and thickness influence the board differently. GSM helps describe the amount of material in the sheet, while PT gives a clearer picture of its physical thickness. In packaging, you often need both measurements to judge stiffness, folding behavior, and finishing performance accurately.

Thickness and Stiffness

For folding cartons and paperboard packaging, thickness plays a major role in rigidity. At a similar board grade, a thicker sheet usually resists bending better and gives the package a more substantial feel. However, stiffness does not depend on thickness alone. Fiber orientation, density, board structure, and moisture content also influence the result.

This means a heavier GSM does not always produce a stiffer box. For example, a higher-bulk folding carton board can feel stiffer than a denser board with a similar GSM because the extra thickness increases resistance to bending. This is why you should compare board caliper and stiffness data, not GSM alone, when box rigidity matters.

Folding and Creasing

Folding performance depends on whether the crease design matches the board thickness. Thicker paperboard needs enough crease depth and width to allow the fibers to bend without cracking, splitting, or creating uneven fold lines. If the crease does not match the board thickness, the finished carton may spring back, bulge, or lose its intended shape. A change from 14 pt to 18 pt board, for instance, may require a different creasing setup because the thicker sheet needs more room to fold.

PT gives a more direct reference for the sheet thickness that the die-cutting and creasing setup must accommodate. GSM remains useful for identifying the board grade and grammage, but thickness, stiffness, grain direction, and crease design have a more direct influence on folding performance.

Printing and Surface Finishing

For premium packaging boxes, GSM and paperboard thickness influence both print handling and the final finishing result. Thicker or more rigid board may need different feeding, pressure, and handling settings, while denser stock can respond differently to embossing, debossing, or foil stamping than a higher-bulk board.

Lamination: Adds a film layer and slightly increases the finished thickness. It can also make folding areas stiffer, so crease settings may need adjustment.
Foil stamping: Requires a stable surface and controlled pressure to keep foil edges clean without crushing the board. Softer, higher-bulk stock may compress more under the stamping die.
Embossing and debossing: Depend on board thickness and compressibility. Thicker, more compressible stock usually supports deeper relief than thin, dense paperboard.
Spot UV and coatings: Add surface build and visual contrast, but they usually change the final thickness less than the base board itself.

Choosing Between GSM and PT for Packaging Specifications

The choice between GSM and PT should match the type of information you need from the material specification. GSM is the better reference when you are comparing paper by grammage or sourcing across suppliers, while PT is more useful when the exact sheet thickness affects structure, converting, or fit. In many packaging projects, one value gives you the starting point and the other provides additional control where needed.

GSM for Paper-Based Materials

GSM is useful when paper weight is the main basis for comparison. It provides a common metric for comparing paper weight across suppliers and markets, which helps keep international sourcing specifications consistent. It also lets you compare lighter and heavier options within the same paper grade before you move on to thickness or stiffness checks.

Common materials specified by GSM include:

Wrapping paper
Printed paper
Specialty paper
Cardstock
Folding carton board

GSM also helps you estimate material usage and keep purchasing specifications consistent across repeated orders. For instance, if you compare 250 gsm and 350 gsm folding carton board from the same grade, the GSM value clearly shows the difference in paper mass per square meter. You can then check thickness separately if the box requires a specific level of rigidity or folding performance.

PT for Thickness-Critical Materials

PT becomes more useful when the packaging design depends on the actual sheet thickness. It defines the sheet thickness directly, making it easier to control structural details such as creasing, fit, and folded dimensions. This makes PT especially useful when the dieline, crease setup, folded panel buildup, or component fit must stay within a defined space.

Typical thickness-critical uses include:

Thick cardstock
Folding carton board with a defined caliper
Paperboard sleeves
Structural paperboard components
Inserts with close fit requirements

A 16 pt board measures 0.016 inch thick, so you can use that value directly when checking crease width, folded panel buildup, slot clearance, or component fit. In these cases, PT gives you information that GSM cannot provide by itself, because the same GSM can still produce different physical thicknesses depending on the paper stock.

GSM and Thickness Specifications in Product Packaging

Paper weight and thickness specifications vary across different product packaging formats. The right value depends on the material, structure, and level of support the package needs. Common ranges also differ between folding cartons, rigid boxes, and custom inserts, so each format requires its own reference.

Folding Cartons

Folding cartons use printable paperboard that folds directly into the finished box. Common materials include SBS, FBB, and kraft-backed paperboard, with grammages often falling around 250–400 gsm for many retail packaging. This range covers product boxes for cosmetics, personal care items, food, and other consumer goods. GSM usually serves as the main material reference, while you can confirm thickness separately when the carton needs tighter control over stiffness, folding behavior, or finished dimensions.

250–300 gsm SBS or FBB: lighter retail cartons for cosmetics, personal care products, small accessories, and other lightweight goods.
300–350 gsm SBS or FBB: a common range for printed product boxes that need a firmer structure and better shelf presentation.
350–400 gsm SBS or FBB: used when the carton needs more body, rigidity, or support for a larger or heavier product.
250–400 gsm kraft paperboard: used for natural-look folding cartons, unbleached packaging, and designs where the kraft surface is part of the visual identity.

Rigid Boxes

Rigid boxes combine a structural greyboard core with a separate wrapping paper, so you should specify these two materials separately. The greyboard creates the box structure, so you normally specify it by physical thickness. The outer wrapping paper serves as the printable and decorative surface, so GSM becomes the more useful specification for that layer. A material callout such as 2.0 mm greyboard + 157 gsm coated art paper gives a much clearer rigid box specification than one GSM value for the whole box.

For the structural board, common thicknesses include:

1.5–2.0 mm greyboard: smaller rigid boxes, cosmetic packaging, jewelry boxes, and lightweight gift boxes.
2.0–2.5 mm greyboard: premium gift boxes, perfume boxes, and larger product boxes that need more rigidity.
2.5–3.0 mm greyboard: larger formats or heavier products that need stronger structural support.

For the outer wrap, the specification usually combines paper type and GSM. Coated art paper commonly falls around 120–157 gsm and works well for printed wraps with lamination, foil stamping, or other decorative finishes. Uncoated, textured, dyed-through, and kraft papers often use a broader range, typically around 120–180 gsm, depending on surface texture, flexibility, and wrapping performance.

Custom Inserts

Custom inserts can hold products in place, divide multiple items, add cushioning, or present printed information inside the box. The right GSM or thickness depends on the insert type and the amount of support it needs to provide. Flat printed pieces usually rely on GSM, while structural inserts may need heavier paperboard, rigid board, or a defined corrugated flute thickness.

Common specifications include:

Printed cards and flat inserts (250–350 gsm): Thank-you cards, instruction cards, warranty cards, product cards, and branded inserts.
Folded or die-cut paperboard inserts (300–400 gsm): Dividers, raised platforms, folded trays, and die-cut product holders.
Corrugated inserts (about 1.6 mm E flute, 3.2 mm B flute, or 4.8 mm A flute): Cushioning and structural support for shipping fragile products that need more protection.
Rigid paperboard inserts (about 1.0–2.0 mm board): Fixed cavities, presentation trays, and support structures for heavier or more delicate products.

Need Help Choosing the Right Paper Weight and Thickness for Custom Packaging?

GSM and PT give you two different ways to evaluate paper and paperboard for packaging. GSM tells you the material weight per square meter, while PT tells you the physical thickness. Because density, fiber structure, coating, and paperboard construction can change thickness at the same GSM, you should treat GSM-to-PT conversions as reference values rather than fixed equivalents.

Gentlever can help you translate these specifications into a practical packaging solution. We review your box structure, product weight, paper or board type, printing, and finishing requirements, then recommend suitable GSM, PT, or board thickness for folding cartons, rigid boxes, and custom inserts. Send us your product dimensions, box size, quantity, artwork or reference design, and preferred finish to receive material recommendations, sampling support, and a custom quotation.

FAQs

1. How many pt is 300 gsm paper?

300 gsm paper can vary widely in thickness, but many dense cardstock grades fall around 12–16 pt. High-bulk paperboard can be considerably thicker. For an exact PT value, check the caliper of the specific paper stock.

2. What is 350 gsm in pt?

350 gsm paperboard does not have one fixed PT value. Many dense cardstock stocks fall around 14–16 pt, while high-bulk boards can be substantially thicker. The exact PT depends on the paper grade and density.

3. How many gsm is 16 pt cardstock?

16 pt cardstock typically falls somewhere around 350–400 gsm. The PT value fixes the sheet at 0.016 inch thick, but the corresponding GSM changes with the stock’s density and construction.

4. What gsm is commonly used for packaging boxes?

Many folding cartons use paperboard around 250–400 gsm. Lighter cartons often use the lower end of this range, while premium retail cartons and larger boxes usually need heavier grades.

5. Is 16 pt cardstock suitable for packaging boxes?

Yes, 16 pt cardstock can work well for folding cartons, sleeves, and other paperboard packaging. Its suitability still depends on the box size, product weight, board stiffness, and crease design.

6. Should I specify gsm or thickness when ordering custom boxes?