Grams per square metre. The weight of one square metre of that paper. That is the entire definition, and everything people believe about it beyond that is inference.
What each range feels like
| GSM | Where you have held it |
|---|---|
| 70–90 | Office printer paper, a newspaper insert |
| 100–130 | A flyer, a cheap magazine |
| 130–170 | A good magazine page |
| 200–250 | A greetings card, an album page |
| 300 | A postcard, a business card, a cover |
| 350+ | Rigid. Packaging territory |
Ours: 170 GSM magazine inner pages, 250 GSM album inner pages, 300 GSM magazine covers, prints and cards. The albums and diaries have hard covers, which are a different construction altogether rather than a heavier paper.
What higher GSM actually buys
Three real things, and they are worth knowing individually rather than as “better”.
1. Opacity. A heavier sheet is more opaque, so the photograph on the other side does not ghost through. This is the main reason inner pages are 170 rather than 130 — below about 150 GSM, a dark photograph shows faintly through the page.
2. Stiffness. A page that holds itself when turned, and a cover that does not curl. This is what 300 GSM is for.
3. The feel. Genuine and hard to quantify. Heavier paper reads as more considered before anybody looks at what is printed on it.
What it does not buy
⚠️ Not print quality. The image quality comes from the file and the printing, not the weight of what it lands on. A poor photograph on 300 GSM is a poor photograph on nice paper.
Not longevity, directly. What degrades a print is light, humidity and handling. A heavier sheet survives handling better; it does not resist fading. How long do printed photos actually last →
Not a finish. GSM says nothing about matte or gloss, which is the difference you will actually notice every time you open it. Matte, gloss and satin compared →
Why heavier is not simply better for inner pages
There is a ceiling, and it is not cost.
A 300 GSM inner page does not turn properly. It resists, it does not lie flat in a saddle-stitched book, and forty of them is a brick rather than a magazine.
Inner pages want to be turned; covers want to be rigid. That is why the two numbers are different and why “we use 300 GSM throughout” would be a worse product rather than a better one.
Page count changes how the same GSM feels. An 8-page magazine is mostly its cover; a 40-page one at the same 170 GSM is noticeably firmer in the hand, because forty pages support each other. So a thin-feeling small magazine is not lighter paper — it is fewer sheets of it.
Weight is not thickness
GSM is how heavy a square metre of the paper is. How thick it is — its caliper, measured in microns — is a separate number, and two papers of the same weight can differ in thickness quite a lot.
Coated papers are denser. The smooth coating that makes photographs sharp packs a lot of weight into a thin sheet, so a coated 170 GSM page can be thinner than an uncoated 150 GSM one.
Uncoated and bulky papers are the reverse — lighter for their thickness, softer in the hand, and often more see-through than their feel suggests.
Stiffness is a third thing again, decided by the fibre and the coating as much as the weight. That is why “300 GSM” from two different sellers can feel like two different papers: both statements are true, and neither tells you the whole of it.
The other units you will meet
Listings written for other countries use different numbers, and they do not convert to GSM on a single scale:
| You see | What it measures | Rough GSM equivalent |
|---|---|---|
| GSM or g/m² | Weight of one square metre | — |
| “lb text” (US) | Weight of a ream of text-size sheets | Multiply by about 1.5: 100 lb text ≈ 150 GSM |
| “lb cover” (US) | Weight of a ream of cover-size sheets | Multiply by about 2.7: 100 lb cover ≈ 270 GSM |
| “pt” (US) | Thickness, in thousandths of an inch | None — it is a thickness, not a weight |
| Microns (µm) | Thickness | None — again a thickness |
⚠️ The trap is “lb” without the word after it. 80 lb text is a light page; 80 lb cover is card. The same number means paper of very different weights depending on which scale it is on.
Using it to compare sellers
GSM is the easiest specification to quote, which is exactly why it is quoted most.
Ask about the finish and the binding too. A seller who says “300 GSM” and nothing else has told you one third of what decides how the object feels. How to judge paper quality → · Photo book binding types →
Reading a listing, line by line:
| The listing says | What to infer, or ask |
|---|---|
| “300 GSM pages” on a stapled book | Pages that heavy tend to crack at a fold — ask whether 300 is really the cover |
| “Premium 350 GSM” and nothing else | Probably the cover; the pages you actually turn are unstated |
| Inner pages at 130 GSM or below | Expect a dark photograph to ghost through onto the next page |
| One figure for the whole book | Ask for the cover and the inner pages separately |
| “Premium paper”, no figure at all | Ask for the weight and the finish, by name |
None of these makes a book good or bad on its own. Each is a question the seller should be able to answer in one line.
The comparison nobody makes
Sellers quote GSM against each other. The more useful comparison is GSM against what the paper has to do.
- A page that folds through a spine has a ceiling of about 200 GSM.
- A page that does not fold has no ceiling worth caring about.
- A cover has a floor — below about 250 GSM it will not hold its shape.
- A loose print that gets handled wants 300 GSM whatever else is true.
Read that way, our three numbers are not a scale from worse to better. They are the answers to four different jobs, and a seller using one number everywhere has either one job or has not thought about it.
Frequently asked
What does GSM mean? Grams per square metre — the weight of a square metre of that paper. It is a weight, not a quality score.
Is higher GSM better? For a cover, yes. For inner pages there is a ceiling — above about 200 GSM the pages stop turning properly.
What GSM is good for a photo book? Around 170 for inner pages and 300 for a cover, which is what we use.
Does GSM affect print quality? No. Image quality comes from the file and the printing. GSM affects opacity, stiffness and feel.
Why are your covers and pages different weights? Covers need to be rigid and pages need to turn. One number for both would make a worse object.
Part of our guide to paper and printing. See also: matte, gloss and satin compared and how to judge paper quality.
170 GSM pages, 300 GSM covers: Photo magazines from ₹499 · All 12 keepsakes