Paper Weight 101 Guide


Navigating paper weights can feel like trying to learn a new language where everyone is shouting different numbers at you. Whether you’re an illustrator looking for that perfect "tooth" or a journaler tired of ink bleeding through the page, understanding these measurements is the first step to stationery nirvana.
Here is your Paper Weight 101 guide.

1. The Big Three: GSM vs. LB vs. KG

The reason paper weights are so confusing is that different regions and industries use different systems.

 GSM (Grams per Square Meter)

    • What it is: The metric standard used globally. It measures how much a single square meter (1m×1m) of that paper weighs.
    • Why it's great: It is consistent. 100 GSM is 100 GSM, regardless of the size or type of paper. It is the easiest way to compare thickness across brands.

LB (Pounds)

    • What it is: The US standard. It measures the weight of a "ream" (usually 500 sheets) of paper in its uncut "basis size."
    • Why it's tricky: The "basis size" changes depending on the paper type. 80 lb "Text" paper is much thinner than 80 lb "Cover" (cardstock) paper. This is why you'll often see "80lb Text" or "100lb Cover."

KG (Kilograms)

    • What it is: Primarily used in Japan (B-base weight). Similar to the LB system, it’s the weight of 1,000 sheets of paper cut to a specific Japanese industry standard size.
    • Why it's used: You’ll see this mostly on high-end Japanese papers like Midori or Tomoe River.

Pro-Tip: If you want a universal "thickness" gauge, look for the GSM. It’s the most reliable way to tell if a paper is "beefy" or “wispy.”


2. Understanding Paper Weight (GSM)

The weight of paper, measured in grams per square metre (GSM), determines its thickness and durability against erasing, layering, and moisture. 

Under 90gsm — use with caution for ink work

Standard printer paper is 80gsm. Cheap sketchpad paper is typically 70–80gsm. At these weights, liquid ink from a loaded dip pen or a brush pen will bleed through to the reverse side of the sheet, feather outward into the paper fibres, or both.

This does not mean you can't use lightweight paper for ink work. Tomoe River, the paper famously used in Hobonichi planners, is 52gsm — considerably lighter than printer paper — and handles fountain pen inks beautifully because of how it's manufactured. Weight alone does not determine suitability. But for beginners using a loaded dip pen for the first time, lightweight paper amplifies every mistake.

The practical rule for your first sessions: use paper of at least 90gsm. The Stillman & Birn Zeta and Beta sketchbooks we stock are 270gsm — which feels almost extravagant for a beginner but means you can work confidently without worrying about bleed-through.

90–150gsm — the working range for most illustration

This is where most illustration paper sits. Heavy enough to handle a loaded nib without bleeding, light enough to handle easily in a sketchbook format. Rhodia paper at 90gsm is the standard recommendation for calligraphy practice. Stillman & Birn Beta at 270gsm handles multiple wet washes over pen linework without buckling.

Above 200gsm — for mixed media and wash work

If you're working with ink washes — applying diluted ink with a brush in broad strokes after the pen linework — you need paper that won't buckle under the water. Arches Aquarelle Hot Press at 300gsm is the professional standard for botanical illustration and mixed-media pen and wash work. At this weight the paper barely moves under a full wet wash.

 

3. Texture & Surface Finish

The "tooth" or grain of the paper dictates how much pigment it "grabs" and how smoothly your pen glides.

This terminology appears on watercolour paper and heavier cartridge papers. Hot press means the paper has been pressed smooth during manufacture. Cold press means it has some surface texture.

For dip pen work, hot press is almost always preferable. The nib moves across a smooth surface without catching on fibres. On a cold press surface, a very fine nib — a Maru nib, for instance — will occasionally catch on the paper texture and produce an unwanted thick stroke.

For calligraphy, hot press is essential. A flexible pointed nib on textured paper is difficult to control even for experienced practitioners.

For brush pen work, smooth is better. Textured paper frays brush pen tips faster.

 

4. Archival & Environmental Considerations

  • Acid-Free: Always ensure your paper is acid-free to prevent yellowing or deterioration over time.
  • Cotton vs. Wood Pulp: 100% Cotton paper is the gold standard for professional work; it is stronger, more absorbent, and allows for extensive "scrubbing" and lifting of colour. Wood-free or wood-pulp papers are excellent, cost-effective alternatives for students

The one mistake most beginners make

Buying a cheap sketchbook and then concluding that the ink, the nib, or their own technique is the problem when the actual issue is that the paper is too lightweight and too absorbent for the tools they're using.

Test any new paper with a swatch before committing your work to it. Load a nib, draw a few lines, wait thirty seconds, turn the page over. If you can read the lines from the reverse, the paper is too lightweight or too absorbent for that ink and nib combination. This is not a failure. It is information.