Paper Weight vs Paper Thickness: Why They’re Not the Same

If you’ve ever ordered print materials, you’ve probably seen terms like GSM (grams per square metre) and microns or caliper used to describe paper. Many people assume weight and thickness are interchangeable—but they’re not.

Understanding the difference can help you choose paper that not only looks right but also feels right for your project.

Paper Weight (GSM)

Paper weight is measured in GSM (grams per square metre). It tells you how much a single sheet of paper would weigh if it measured one square metre.

• Lower GSM = lighter paper (e.g., 80gsm office sheets).
• Higher GSM = heavier paper (e.g., 350gsm business cards).

👉 GSM is all about weight, not thickness.

Paper Thickness (Caliper / Microns)

Paper thickness, often called caliper, is measured in microns (1 micron = 1/1000 of a millimetre). It tells you how thick a single sheet of paper is when measured with precision tools.

• Example: An 80gsm sheet might be around 100 microns thick.
• A 300gsm coated card could be about 250–300 microns.

👉 Thickness is a physical measurement, not a weight.

Why the Same GSM Can Feel Different

Here’s where it gets interesting: two papers with the same GSM can feel completely different in the hand.

That’s because:

• Coated paper is denser → thinner for the same GSM.
• Uncoated paper is bulkier → thicker for the same GSM.
• Specialty papers (like textured or recycled) may also bulk differently.

So a 300gsm glossy flyer might feel slimmer than a 300gsm uncoated invitation, even though the weight is the same.

Practical Example

• 80gsm uncoated paper: Everyday office printing (lightweight, easy to fold).
• 80gsm coated paper: Feels thinner because of higher density, often used for magazines.
• 300gsm silk-coated card: Smooth and sturdy, great for brochures.
• 300gsm uncoated card: Feels chunkier, often chosen for invitations or premium stationery.

Why It Matters

• Mailing weight: Postage is charged by weight, not thickness.
• Design feel: Customers notice how “substantial” a product feels in hand.
• Printer compatibility: Some machines struggle with thicker stocks, even at the same GSM.

Final Thoughts

Weight and thickness are related, but not identical. GSM tells you how heavy the paper is, while microns (thickness) tell you how bulky it feels. The right choice depends on your project—whether you need lightweight and flexible, or thick and luxurious.