Pick up a ream of office paper and the wrapper says 80gsm. Pick up a pack of blank greetings cards and it says 300gsm. That one number tells you how heavy the paper is, how stiff it feels and whether your printer will feed it without a fuss.
If you have ever asked yourself what is GSM, or spotted it written as gm/2 or g/m² and wondered whether they are different things, they are not. All three mean grams per square metre. This guide covers what the figure means, the weights used for everyday jobs and what goes wrong when paper is too thick for your machine.
For a wider look at paper types, sizes and finishes, read our Complete Guide To Printer Paper: Know What You Are Buying.
What GSM Means
GSM stands for grams per square metre. Picture a sheet of paper measuring exactly one metre by one metre. Weigh it, and the result in grams is its GSM. An 80gsm sheet weighs 80 grams and a 300gsm sheet weighs 300 grams.
You will never print on a sheet that big, of course. An A4 page covers about one sixteenth of a square metre, so an 80gsm A4 sheet weighs roughly 5 grams. A 300gsm A4 sheet weighs closer to 19 grams. That is almost four times the weight, which is why card behaves so differently in a printer. Paper makers weigh their samples using a standard method (ISO 536), so the figure on one brand’s pack compares fairly with another’s. You can read more about the measurement on the grammage page on Wikipedia.
Weight Is Not The Same As Thickness
GSM measures weight, not thickness. Thickness is measured in microns, where one micron is a thousandth of a millimetre. In the US you will also see it called caliper.
The two usually rise together, but not always. Standard 80gsm uncoated copy paper is around 100 microns thick, while 300gsm uncoated board is around 350 microns. Coated paper is denser, so a 100gsm coated sheet can be as thin as 87 microns. Even two brands of 100gsm paper can differ in thickness, depending on the pulp and how tightly it is pressed.
For everyday buying, though, GSM works as a stand-in for thickness. It is also the figure printer makers use when they quote a limit, so it is the one to check.
GSM, gm/2 And g/m²: Different Names For The Same Thing
Paper weight turns up under several labels, and they cause more confusion than they should. GSM, gsm, g/m² and gm/2 all mean grams per square metre.
The proper written form is g/m², with a small raised 2 to show “squared”. When that superscript gets lost in a spec sheet, an email or a search box, you end up with g/m2, gm2 or gm/2. It is the same measurement typed a different way. In the UK, GSM is the everyday term and the one printed on most packaging. You may also see “meter” spelt the US way, but the unit is identical.
| Term | What It Means | Where You Will See It |
|---|---|---|
| GSM or gsm | Grams per square metre | Paper packaging, printer spec sheets and online shops |
| g/m² | Grams per square metre, in its formal written form | Technical data sheets and manufacturer specifications |
| gm/2, g/m2 or gm2 | Grams per square metre, typed without the superscript | Older listings, emails and search queries |
| lb (basis weight) | The weight of a 500-sheet ream at its uncut size, used in the US | US paper packs. As a guide, 20lb bond is about 75gsm and 24lb is about 90gsm |
| Microns or caliper | Thickness rather than weight, where 1,000 microns equals 1mm | Card, labels and specialist stock |
Common Paper Weights And What They Are Used For
Paper weights fall into loose bands. Match your job to the band in the table and you will land close to the right number.
| GSM | How It Feels | Typical Uses |
|---|---|---|
| 35 to 55 | Thin and almost see-through | Newsprint and rough drafts |
| 70 to 90 | Light and flexible | Everyday printing and copying. 80gsm is the office standard |
| 90 to 100 | Slightly heavier, with less show-through | Reports, presentations and letters |
| 100 to 120 | Crisp and smooth | Letterheads and double-sided documents |
| 120 to 160 | Noticeably stiff | Flyers, takeaway menus, posters and certificates |
| 160 to 250 | Light card | Leaflets, invitations, restaurant menus and craft projects |
| 250 to 300 | Stiff card that still bends | Magazine covers, premium flyers and greetings cards (around 300gsm) |
| 350 to 450 | Thick card that resists bending | Business cards (350 to 400gsm), postcards and table talkers |
Greetings Cards And Business Cards
The 300gsm figure for greetings cards is worth remembering. It is stiff enough to stand on a shelf, yet light enough to fold once with a clean crease. Score the fold first if your printer allows it, because heavy card can crack along an unscored line.
Meanwhile, business cards sit higher, at 350 to 400gsm, because they have to survive a wallet. Both weights are far above what a standard office printer expects, so check the limits covered further down before you load them. If you print cards regularly, our guide to the best printers for printing on card and our card printing range are good places to start.
Why Paper Weight Matters
Weight changes the result in four ways. First, feel. A heavier sheet suggests quality, which is why letterheads and invitations use more than 80gsm. Second, show-through. Text printed on one side of a thin 70gsm sheet can ghost through to the other, so double-sided documents look better on 100gsm.
Third, durability. A menu, a flyer or a card gets handled, and heavier stock survives it. Finally, cost. Heavier paper costs more per sheet and weighs more in the post.
Heavier is not automatically better, though. A 300gsm letter is awkward to fold, sits badly in a filing folder and puts far more strain on your printer than 80gsm paper does.
What Happens When Paper Is Too Thick For Your Printer
Every printer has a maximum GSM, and it comes down to how the sheet travels through the machine. Rollers pull the paper from the tray, bend it around a curved path, feed it past the print mechanism and push it out to the exit tray. Thick paper resists that bend. The further past the limit you go, the more problems appear.
Paper Jams And Misfeeds
In fact, jams are the most common result. A stiff sheet fails to follow the curve, catches on a guide and stops halfway through. Rollers can also slip on heavy stock and pull nothing at all, or grab two sheets together and jam them deeper inside. Clearing a jam means tugging paper against the rollers, and that is where damage often starts.
Smudged And Poorly Fixed Prints
A laser printer fuses toner to the page with heat and pressure. Thick paper soaks up more of that heat, so the toner can sit loosely on the surface and rub off or flake. However, inkjets have their own problem. Heavy uncoated card can hold more ink than it dries, so the ink pools and smears. In some machines, thick stock can also brush the print head and leave streaks across the page.
Skewed Prints, Marks And Extra Wear
Additionally, thick paper often enters at a slight angle, so the print lands crooked. Feed rollers can leave scuff marks on card as they fight to grip it. Regularly running over-limit stock also wears the pickup rollers and separation pads faster, and it stresses the fuser in a laser printer, which is one of the most expensive parts to replace.
However, one stray sheet will not wreck a printer. Using paper beyond the stated limit week after week can shorten its life.
The Opposite Problem: Paper That Is Too Thin
On the other hand, very light paper causes trouble too. Cheap 60 to 70gsm sheets curl, cockle when they meet wet ink and double-feed more easily. For everyday printing, 80gsm is a sensible floor.
Typical GSM Limits By Printer Type
Limits vary by model, so treat this table as a rough guide only. Your printer’s own spec sheet always wins.
| Printer Type | Typical Limit | Notes |
|---|---|---|
| Inkjet printer | Up to about 300gsm | A rear or straight-through feed gives the best results on card |
| Laser printer (main tray) | Often around 160 to 220gsm | The fuser and curved paper path set the limit |
| Laser printer (bypass tray) | Often higher than the main tray | Uses a straighter path, so it copes better with card. Check the manual |
| Photo and wide-format inkjet | Often 300gsm or more | Built for thicker photo and fine art media |
If you use a laser printer for card, our guide to the maximum GSM that laser printers will accept goes into far more detail.
How To Check Your Printer’s Maximum GSM
Spend two minutes on the checks below before you load anything heavier than 100gsm.
- Look in the spec sheet or manual for “media weight”, “paper weight” or “supported media”.
- Check each tray separately. The main cassette, the bypass tray and any rear feed usually have different limits.
- Set the media type in the print settings to heavy paper, card or thick. The printer then slows down and, on a laser, raises the fuser temperature.
- Test with a few sheets first, feeding one at a time through the bypass or rear tray.
If your projects need heavier stock than your printer can take, buy a printer that suits the job instead of forcing the one you have.
Conclusion: Match The Paper To The Printer
GSM, gm/2 and g/m² are three ways of writing the same measurement: the weight in grams of one square metre of paper. The higher the number, the heavier and usually thicker the sheet. That runs from 80gsm office paper up to 300gsm greetings cards and 400gsm business cards. Weight and thickness are not identical, but for choosing paper the GSM figure is the one that counts, because it is the one printer makers quote.
In practice, the advice is simple. Check your printer’s limit before you buy, note which tray it applies to and stay inside it. Go over that limit and you risk jams, smudged prints and extra wear on the rollers and fuser. Nobody wants a repair bill over a pack of cards. If your projects need heavier stock than your current machine can take, that is the moment to look at a different printer. When you are ready to stock up, browse our printer paper range, and our team can help you match paper to printer if you are unsure.
Frequently Asked Questions
What Does GSM Stand For On Paper?
GSM stands for grams per square metre. It tells you how much a one metre by one metre sheet of that paper would weigh, so a higher number means heavier paper.
Is gm/2 The Same As GSM?
Yes. The gm/2 spelling is a common way of typing g/m² when the superscript is missing, and both mean grams per square metre. Similarly, g/m2 and gm2 all describe the same measurement as GSM.
What GSM Is Standard Printer Paper?
Most office paper is 80gsm. Some packs use 75gsm, and letters or reports often use 90 to 100gsm for a firmer feel. Every home and office printer handles these weights.
What GSM Is Best For Greetings Cards?
Around 300gsm suits most greetings cards. It is stiff enough to stand up, yet it still folds cleanly, especially if you score the fold first. Check that your printer accepts 300gsm before you buy a pack.
Can I Use 300gsm Paper In A Laser Printer?
It depends on the model. Many laser printers top out at around 160 to 220gsm through the main tray, although a bypass tray may take heavier card. Read the manual first, and see our guide to the maximum GSM for laser printers for more.
What Happens If Paper Is Too Thick For My Printer?
You will most likely see paper jams and misfeeds. Toner or ink may also smudge or fail to fix properly, and the sheet can pick up marks from the rollers. In addition, regular use of over-limit paper wears the rollers and, in a laser, the fuser.
How Do I Find My Printer’s Maximum GSM?
First, open the spec sheet or manual and look for media weight or paper weight. Each tray often has its own limit, so check the one you plan to use. Our team can also help if you give us your printer’s model number.
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