A Guide to Paper Weight and Thickness
A fine art print is not a poster. You're buying craftsmanship and material quality that are part of the art itself - and that quality is a choice, not a given. A poster is standardised and fixed but a fine art print can be made hundreds of different ways. Paper choice shifting how the image feels, reads, and lives on your wall. That's why it's worth understanding a few key metrics about papers - they'll give an idea how one paper differs from another before it arrives at your door.
You know paper the moment you touch it. Soft or stiff, light or heavy, matte or glossy — the hands make that judgment faster than words do. But what happens when you can’t touch the paper, like when buying prints online? What you're left with is a picture of a picture and a few lines of product description. How do you know what you’re actually getting?
There are three main metrics directly affect how a printed image will look: paper coating, weight (measured in GSM – grams per square meter), and thickness (measured in microns). These influence how the ink sits, how colors appear, and how the paper handles. There are also secondary factors like brightness, opacity, and reflectiveness of a paper, which can subtly shift the feel of a print, but they’re not as critical as the core three.
We’ve already looked at coatings - glossy, semi-gloss, matte, and so on, which play a big role in how a print looks. Recall that coating is essentially a layer on top of the base paper that controls how ink is absorbed. Without a coating ink would bleed into the fibers, causing dull, blurry prints with no sharpness or detail. But coating also affects contrast, brightness, depth of blacks, and how reflective the surface is. But even within one category of coating - say, glossy - there’s a wide range. An RC glossy and a Baryta glossy may both shine, but they look and feel very different because of the underlying base. What matters here is that coating alone won’t tell you how thick or heavy a paper is. A heavier, more rigid paper can give a print a sense of presence and depth, while thinner papers may feel more fragile or casual, even if the coating is the same.
Why does this matter? Because paper is the structural foundation of a print. Just like a building needs the right materials to support its design, a print needs the right paper to support the image. Some images call for light, delicate papers, others demand something thick and weighty. Whatever the printer’s vision, the foundation has to carry it. It needs to do so at any size, but specially in large sizes. If the paper can’t hold the image, physically or visually, the print falls flat.
Larger prints need heavier paper to stay stable and flat. As the size increases, so does the risk of warping or buckling, especially with high ink coverage. Thicker paper adds rigidity and helps the print hold its shape. Added thickness is also allowing to absorb more ink for deeper blacks and richer tones. Weight alone is not ver accurate description. For example, RC-based papers tend to thin but their heavy plastic base is heavier than paper. In contrast, cotton papers might be thicker but still weigh less, giving a softer, more flexible feel. So both weight and thickness matter, but in different ways. That’s why you have to understand the materials used to produce a print. What really helps cut through the noise are the measurable specs: GSM for weight and microns for thickness. But to make sense of them, you need a reference point, something familiar to compare against.
The Reference Point: Standard Office Paper
Let’s take something we all know and can relate to - standard office or copier paper. Most of office paper is 80 GSM and about 100 microns thick. That means one square meter of it weighs 80 grams, and stacking 10 sheets gives you about 1 millimeter in total thickness. It’s lightweight, thin, and flexible designed for typewriters, copy machines and text prints. This gives you a useful baseline if you’ve never touched fine art or photo papers.
For example, take a fine art paper rated at 320 GSM and 300 microns. Without prior experience, those numbers don’t mean much. But with office paper as a reference, it becomes easy. This paper is about four times heavier (like four sheets of copier paper: 320/80) and three times thicker (like a stack of three: 300/100). That difference is immediately felt in weight, rigidity, and how the print holds itself. Heavier paper holds more ink, resists buckling, and has a stronger physical presence. With that reference in mind, let’s look closer at how GSM and micron values actually shape the experience of a print.
What is GSM?
GSM (grams per square meter) measures the mass per unit area—specifically, the weight of one square meter of paper. How large is one square meter? About 16 A4 pages. So if an A4 photo paper is 300 gsm, each page should weigh approximately 19 grams (300/16). Paper weight increases with each coating layer, so budget papers tend to weigh less than premium papers, which use multiple inkjet receptor coatings that add mass. But weight alone can be deceiving. A 300 gsm cotton rag paper can feel soft and thick, while a 300 gsm RC (resin-coated) photo paper can feel thin and stiff. Same weight, completely different feel, so we need a complimentary metric to catch the difference between the two papers.
What is a Micron?
Hence, we have another measure for paper - its thickness, measured in micron (µm). One micron is one-thousandth of a millimeter (1/1000). Sometimes it is written as fraction of a millimeter instead. For example 0.26mm instead of 260 micron (µm). Typical photo papers range from 180–400 µm, while heavier fine-art papers and boards can reach 600 microns or more.
In practice, micron reveals what GSM alone cannot:
How stiff the sheet will feel
How well it resists curling and bending
How "substantial" it feels in hand
How it behaves when mounted or framed
The Relationship Between GSM and Microns
GSM and micron are related but not the same, and their relationship varies depending on paper density.
If two papers have the same GSM but different microns, the thicker one is less dense—more air, more bulk, more "body." If two papers have the same micron but different GSM, the heavier one is denser—more fiber packed into the same space, more coating layers applied.
Micron is often closer to the felt quality of the paper together with the coating and surface type. While GSM relates more to paper type and the amount of coating. What often gets overlooked is stiffness versus thickness. A cotton rag matte paper at 450 microns can feel softer and more flexible than a 350 micron baryta paper with a dense coating. Baryta is always more stift as it is a clay-type coating on top the paper. For stiffness there is no agreed metric, so this one is purely experienced based.
In summary
GSM tells you how heavy it is. Micron tells you how real it feels. Understanding both metrics gives you a complete picture.
High GSM + Low Micron or micron the same as GSM → dense, hard, often resin-coated. For example, Ilford Galerie Smooth Pearl (310gsm, 310 micron)
Lower GSM + High Micron → bulky, airy, cotton or alpha-cellulose. For example, Canson Arches 88 Rag (310gsm, 485 micron)
High GSM + High Micron → thick, luxurious, board-like fine art stock or canvas. For example, Hahnemühle Museum Etching (350gsm, 600 micron)
Next time you order paper, check both numbers—then order sample packs from 2-3 manufacturers. The only measurement that matters more than GSM or microns is how the paper feels in your hand with your image on it.
One more thing. While GSM has not been converted to pounds, micron was converted to inches. In US it is expressed in Mil - means thousandths of an inch where 1 mil ≈ 25.4 µm. So to convert mil to µm we have to multiply Mil by 25. For example 19mil paper is about 480 microns (um) or 0.48mm. Furthermore, sometimes instead of mil it is written as 0.019” as fraction of an inch. So be careful when you read the spec - it is very easy to confuse 19mil with 0.19mm which will make you think that the paper is too thin.