GSM stands for grams per square meter. It is the weight of one square meter of a paper, and it is the standard way to compare paper weight. Typical office paper is about 80 gsm, so journal pages of 100 to 120 gsm feel noticeably heavier. Higher gsm usually means a sturdier sheet, but not always a thicker one.
Key Takeaways
- GSM measures mass per area, grams per square meter, regardless of how big the sheet is cut.
- Typical office paper is about 80 gsm, according to the grammage reference, which makes it a handy reference point for journal paper.
- US paper is often sold in pounds, and a pound rating means different things for bond, text and cover paper.
- GSM does not decide bleed-through on its own. Sizing, surface finish and your ink matter as much.
- A two-minute swatch test on the back page tells you more about a notebook than any number on the label.
What gsm means
GSM is grammage, the mass of paper per unit area, written as grams per square meter (g/m2). It describes the paper stock itself, not the size of the sheet, so a 100 gsm A5 page and a 100 gsm A4 page are the same paper, just cut differently.
The grammage reference defines it as the weight in grams per square meter regardless of the paper's thickness, and notes that typical office paper is 80 g/m2, which makes an A4 sheet weigh about 5 grams. There is also an international test method for measuring it: ISO 536:2019 specifies how to determine the grammage of paper and board, so gsm values from different mills are measured the same way.
In a notebook listing, gsm is the quickest way to compare paper. If one journal lists 80 gsm and another 120 gsm, the second has 50 percent more paper fiber in every square meter, and you will feel the difference when you turn the pages.
The gsm ladder: what each weight handles
As a rule of thumb, paper around 80 gsm is fine for pencil and ballpoint, 100 to 120 gsm handles most everyday journaling pens, and heavier writing papers give you more room for wet inks, markers and light collage. Treat the table below as a starting point and always test your own pens.
We anchored the ladder to two kinds of reference: the 80 gsm office paper figure from the grammage reference, and the paper weights listed on our own notebooks, so you can see where real products sit.
| Paper weight | Where you see it | Usually comfortable for | Test first with |
|---|---|---|---|
| Under 80 gsm | Lightweight papers, thin dictionary-style pages | Pencil, fine ballpoint | Gel pens, fountain pens, markers |
| 80 gsm | Typical office and printer paper | Pencil, ballpoint, many fine gel pens | Fountain pens, felt-tip markers |
| 100 gsm | Our B5 pebble grain notebook, linen hardcover planner and many of our inserts | Ballpoint, gel, rollerball, fine liners | Broad fountain pen nibs, brush markers |
| 120 gsm | The kraft pages in our cowhide leather sketchbook journal and thick cowhide journal | Everyday pens, pencil sketching, glue sticks, light collage | Watercolor, heavy markers |
| 160 g | Our A5 floral dot grid journal (paper weight per supplier) | Everyday pens, with more margin for wetter inks and light layering | Very wet inks, alcohol markers, watercolor |
| Card and cover stock | Dividers, tabs, covers, tags | Stamping, tabs, pockets and dashboards | Writing comfort; very stiff sheets can be hard to fold |
The "usually comfortable" column is our practical guidance, not a guarantee. Two papers with the same gsm can behave very differently, which is the subject of the section after next.
GSM vs pounds: converting US paper weights
US paper is often labeled in pounds, the weight of a 500-sheet ream at a basis size that depends on the paper type. Because bond, text and cover paper use different basis sizes, "80 lb" can mean very different papers. Converting to gsm puts them all on one scale.
The grammage reference lists the US basis sizes: 17 x 22 in for bond and writing paper, 25 x 38 in for book and text paper, and 20 x 26 in for cover stock, each counted per 500-sheet ream. Working through the area of each ream gives these conversion factors and equivalents (rounded):
| Paper type (basis size) | Multiply lb by | Common US weights | About gsm |
|---|---|---|---|
| Bond / writing (17 x 22 in) | 3.76 | 20 lb, 24 lb, 28 lb, 32 lb | 75, 90, 105, 120 |
| Text / book (25 x 38 in) | 1.48 | 60 lb, 70 lb, 80 lb, 100 lb | 89, 104, 118, 148 |
| Cover (20 x 26 in) | 2.70 | 65 lb, 80 lb, 100 lb | 176, 216, 270 |
So a 100 gsm journal page sits between 24 lb and 28 lb bond, or close to 70 lb text. To go the other way, divide gsm by the same factor. This is why gsm is easier for comparing notebooks: it is one number that means the same thing for every kind of paper.
Why gsm is not the only thing that matters
GSM tells you how much paper there is per square meter, not how the surface treats ink. Bleed-through and feathering depend heavily on sizing and surface finish, and thickness depends on how densely the fibers are packed. A well-sized 80 gsm paper can outperform a poorly sized 120 gsm one with fountain pen ink.
Thickness and density
Weight and thickness are related but not the same. The paper density reference explains that density is calculated by dividing grammage by caliper, the sheet's thickness. Two papers can share the same gsm while one is fluffier and thicker and the other is compressed, smoother and thinner. That is why some 100 gsm notebooks feel thicker than others.
Sizing and surface finish
Sizing is a treatment that reduces how much liquid paper absorbs. The sizing reference describes it as reducing the paper's tendency to absorb liquid so that inks stay on the surface and dry there, and notes it can be added inside the pulp or applied to the surface for high-grade writing papers. For journalers, good sizing is what keeps a wet ink line crisp instead of spreading into the fibers.
Paper type and color
Kraft paper, like the warm natural-tone pages in some of our leather journals, has a different texture and look from bright white paper. Textured surfaces can catch a fine nib or a felt tip differently than smooth ones, and darker pages change how ink colors appear. Neither is better; they just suit different pens and styles.
Your pen and ink
The same paper can handle a fine ballpoint perfectly and struggle with a broad, wet fountain pen nib or a juicy marker. The more ink a pen lays down, the more the paper's sizing and weight are tested. If you mainly use fountain pens, our fountain pen friendly paper checklist goes deeper on what to look for.
How to run a two-minute bleed and ghosting test
Use the last page of the notebook to test every pen you plan to use. Write a short swatch with each, let it dry, then check the back of the page for bleed-through (ink soaking through) and hold it up to the light for ghosting (seeing the writing from the other side).
- Pick the back page. Use the last page or the inside back cover so your test does not interrupt the journal.
- Write a swatch per pen. For each pen, write a word, draw a line and fill a small square. The filled square shows how the paper handles a lot of ink in one place.
- Label each swatch. Note the pen name next to it so you remember which one passed.
- Wait about a minute. Let wet inks dry fully before you judge them. Touch a corner of each swatch to check for smudging.
- Turn the page. Look for dots or patches of ink on the back. That is bleed-through, and it means that pen will mark the next page.
- Hold it to the light. If you can read the writing through the page but no ink came through, that is ghosting. Light ghosting is normal on most journal paper and many people do not mind it.
If a favorite pen bleeds, try it on every other page, use the back side for lighter notes only, or keep that pen for a heavier-paper notebook.
Will 100 gsm paper bleed?
Most everyday pens will not bleed through good 100 gsm journal paper, but it depends on the pen and the paper's sizing. Ballpoint, gel and fine liners are usually fine. Broad fountain pen nibs, brush pens and alcohol markers may still bleed or ghost, so test them first.
100 gsm is a useful middle ground because it is noticeably heavier than 80 gsm office paper yet still thin enough to keep a notebook slim with plenty of pages. Several of our notebooks use it, including the B5 soft PU leather notebook and the linen hardcover planner. If you plan heavy markers, collage or paint, look at 120 gsm and above, and still run the swatch test above.
Frequently asked questions
Will 100gsm paper bleed?
Good 100 gsm journal paper usually does not bleed with ballpoint, gel or fine liner pens. Broad fountain pen nibs, brush pens and alcohol markers can still bleed or ghost, depending on the paper's sizing and how wet the ink is. Test each pen on the last page before you commit.
What is the best type of paper to use with a fountain pen?
Look for smooth, well-sized writing paper rather than chasing a high gsm number. Sizing keeps ink on the surface, which the sizing reference describes as reducing the paper's tendency to absorb liquid. Weight helps with show-through, so 100 gsm and above is a sensible place to start testing.
Is a higher gsm paper better?
Higher gsm paper has more fiber per square meter, so it is heavier and often less see-through, but it is not automatically better. It makes a notebook thicker and heavier for the same number of pages. For everyday writing, 80 to 100 gsm is often enough; for wet inks, markers and collage, heavier paper gives you more margin.
What is the thickness of paper based on gsm?
You cannot get an exact thickness from gsm alone. According to the paper density reference, density equals grammage divided by caliper, so two papers with the same gsm can differ in thickness if one is more tightly compressed. Check the caliper if a listing gives it, or compare in person.
Choose your paper weight with confidence
Now that you can read a gsm number, compare the paper specs on each listing in our notebooks and planners collection, from 100 gsm everyday notebooks to the heavier dot grid journal. For kraft pages and leather covers, browse the leather journals collection, and see our guide on how to choose a leather journal for how paper weight fits into the bigger decision.
US orders ship for a flat $6.99 and free on orders of $79 or more, and unused items can be returned within 14 days of delivery. Paper and size questions are answered on our FAQ page, and our notebook sizes guide helps you pick the page size. When you are ready, start with the notebooks and planners collection.
