Paper Thickness Conversion Chart
Paper thickness is quoted three different ways: GSM (grams per square meter, which is a weight), microns and mils (true thickness), and points, where 1 pt = 0.001 inch. GSM does not convert exactly to thickness because it depends on the density of the sheet, so every GSM conversion is approximate.
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Understanding Paper Thickness in Packaging
When it comes to packaging, “thickness” can mean a dozen different things depending on who you ask. One person says 100 GSM, another says 3 mil, and a third swears by 75 µm. They might all be talking about the same thing—just in different units.
That’s why this paper thickness conversion chart exists: to make life easier for buyers, designers, and production teams who deal with paper, film, or laminates every day. Whether you’re comparing kraft linerboard, art paper, or coated stock for your pouches, this guide translates GSM into real-world thickness you can feel.
What GSM Really Means
GSM (grams per square meter) measures the weight of paper, not its actual thickness. Still, heavier papers usually end up thicker, so printers and converters often use GSM as a shorthand for rigidity or strength.
In flexible packaging, GSM affects:
- Durability: Heavier papers resist tearing and creasing.
- Print quality: Thicker stock allows richer ink coverage.
- Fold & feel: Critical for retail display and perceived quality.
Paper Thickness Conversion Chart (Approximate)
| Paper Type | GSM | Millimeters (mm) | Microns (µm) | Mils |
|---|---|---|---|---|
| Kraft Paper | 40 gsm | 0.06 mm | 60 µm | 2.4 mil |
| 60 gsm | 0.09 mm | 90 µm | 3.5 mil | |
| 80 gsm | 0.12 mm | 120 µm | 4.7 mil | |
| 100 gsm | 0.14 mm | 140 µm | 5.5 mil | |
| 120 gsm | 0.17 mm | 170 µm | 6.7 mil | |
| C2S Art Paper | 80 gsm | 0.07 mm | 70 µm | 2.8 mil |
| 100 gsm | 0.09 mm | 90 µm | 3.5 mil | |
| 128 gsm | 0.12 mm | 120 µm | 4.7 mil | |
| 157 gsm | 0.15 mm | 150 µm | 5.9 mil | |
| Matte Coated Paper | 80 gsm | 0.08 mm | 80 µm | 3.1 mil |
| 100 gsm | 0.10 mm | 100 µm | 3.9 mil | |
| 128 gsm | 0.13 mm | 130 µm | 5.1 mil | |
| 157 gsm | 0.16 mm | 160 µm | 6.3 mil | |
| Wood-Free Offset Paper | 70 gsm | 0.09 mm | 90 µm | 3.5 mil |
| 80 gsm | 0.10 mm | 100 µm | 3.9 mil | |
| 100 gsm | 0.13 mm | 130 µm | 5.1 mil | |
| 120 gsm | 0.15 mm | 150 µm | 5.9 mil |
Note: Values vary slightly by fiber type, moisture, and finishing. Use this as a reference, not a certification chart.
Why Paper Thickness Matters in Packaging
When selecting paper for flexible packaging:
- Kraft liners (80–150 gsm): Strong and recyclable.
- C2S or matte coated stock: Offers print gloss and visual polish.
- Wood-free papers: Ideal for inner layers and labeling.
Heavier isn’t always better—choose based on the product, barrier needs, and machine speed.
Common Conversions in Flexible Packaging
If you’re switching between paper and film lamination, here’s how the numbers translate:
| Unit | Equivalent |
|---|---|
| 1 mil | 25.4 µm |
| 1 µm | 0.001 mm |
| 1 mm | 39.37 mil |
| 1 gsm | no fixed thickness — depends on density (see note below) |
Why there is no single GSM-to-thickness factor. GSM measures weight per square meter, not thickness. Two sheets at the same GSM can differ by 30% in caliper because they differ in density. The real relationship is thickness (mm) = GSM ÷ (density in g/cm³ × 1000). As a rough guide, bulky uncoated and kraft grades run about 1.3–1.6 microns per gsm, while coated grades run about 0.85–1.1 microns per gsm — which is why the coated rows in the tables above are thinner than the kraft rows at the same weight. Always measure or ask your supplier for the actual caliper before you commit to a dieline.
Converting Paper Thickness into Real-World Results
Understanding paper thickness is more than numbers on a chart—it’s how your packaging performs, feels, and protects what’s inside. Whether you’re working with kraft, coated stock, or laminates, knowing the right GSM or micron range keeps your project efficient and on-brand.
Hawk Packaging helps brands take the guesswork out of material selection. From pouch liners to specialty wraps, we match specs that look sharp, run clean, and deliver consistent quality. For help selecting the right paper or laminate, contact our team for quick guidance and a quote.
Frequently Asked Questions
Is GSM the same as thickness?
No. GSM is grams per square meter, which is a weight. Thickness is measured in microns, mils or points. Two sheets at the same GSM can differ by around 30% in thickness because they differ in density.
How do I convert GSM to mm?
Use thickness in mm = GSM divided by (density in g/cm3 x 1000). As a rough guide, bulky uncoated and kraft grades run about 1.3 to 1.6 microns per gsm, while coated grades run about 0.85 to 1.1.
How thick is 300 gsm paper in mm?
Roughly 0.30 to 0.38 mm, depending on the grade. A coated 300 gsm sheet is noticeably thinner than an uncoated or kraft sheet of the same weight.
What is the difference between GSM and pt?
GSM is a weight per unit area; a point is a thickness, equal to 0.001 inch for paperboard. They are not interchangeable without knowing the density of the stock.