Paper reference
Paper Weight Guide: GSM, lb and pt Explained
The three systems used to describe paper weight and thickness — and how to choose the right paper for your print project.
GSM: grams per square meter
GSM (g/m²) is the international standard for paper weight. It states how much one square meter of the paper weighs, independent of the sheet size you buy. Because ISO paper sizes are defined from a one-square-meter A0 sheet, metric sheet weights are trivial to derive: an A4 sheet is 1/16 m², so one A4 sheet of 80 GSM paper weighs exactly 5 grams. You can verify any combination with the sheet weight calculator.
Basis weight: pounds per ream (lb)
The U.S. system weighs 500 sheets — a ream — cut to a basis size that differs by paper grade:
| Category | Basis size | Typical range |
|---|---|---|
| Bond/Writing | 17 × 22 in | 16–40 lb (60.2–150.4 GSM) |
| Text/Book/Offset | 25 × 38 in | 50–120 lb (74.0–177.6 GSM) |
| Cover | 20 × 26 in | 65–130 lb (175.8–351.5 GSM) |
Because each category weighs a different sheet, the same number means different papers: 80 lb Text is a 118.4 GSM brochure paper, while 80 lb Cover is a 216.3 GSM card stock. Convert any value with the GSM to lb and lb to GSM charts, or use the two-way paper weight converter.
Caliper points (pt)
Points measure thickness, not weight: 1 pt = 0.001 inch (0.0254 mm). Card stock in the U.S. is often sold by points — for example "14 pt postcard stock". Thickness and weight correlate but are not equivalent, because coating and fiber density change the ratio. Typical approximate equivalents:
| Caliper | Thickness | Approx. weight |
|---|---|---|
| 8 pt | 0.203 mm | ≈ 190–210 GSM |
| 10 pt | 0.254 mm | ≈ 230–250 GSM |
| 12 pt | 0.305 mm | ≈ 280–300 GSM |
| 14 pt | 0.356 mm | ≈ 330–350 GSM |
| 16 pt | 0.406 mm | ≈ 380–400 GSM |
Approximate values for coated card stocks; uncoated papers can differ noticeably.
Which paper weight should you choose?
| Weight range | Typical uses |
|---|---|
| 35–55 GSM | Newsprint, directory paper |
| 60–80 GSM | Book pages, standard office and copy paper |
| 90–115 GSM | Letterheads, quality documents, magazine pages |
| 120–170 GSM | Flyers, brochures, posters, folded leaflets |
| 180–250 GSM | Light card: postcards, covers, tickets |
| 250–350 GSM | Card stock: business cards, invitations, packaging |
| 350+ GSM | Heavy board: premium cards, tags, boxes |
Two practical checks before ordering: confirm your printer's maximum supported GSM (many office printers stop around 200–250 GSM), and for mailed pieces calculate the finished piece weight with the sheet weight calculator to anticipate postage bands.
Frequently asked questions
What does GSM stand for?
GSM stands for grams per square meter (also written g/m²). It measures the weight of one square meter of paper regardless of sheet size, which makes it easy to compare papers directly.
Is higher GSM better quality?
Higher GSM means heavier, usually thicker and stiffer paper — not automatically better. The right weight depends on the job: 80–100 GSM for documents, 130–170 GSM for flyers, 300+ GSM for cards.
What GSM is card stock?
Card stock typically starts around 200 GSM. Common business cards are 300–400 GSM, and premium boards go higher.
What is the difference between pt and lb?
Points (pt) measure thickness — 1 pt = 0.001 inch of caliper. Pounds (lb) measure the weight of 500 basis-size sheets. Two papers with the same lb can have different pt depending on density and finish.
What weight is standard printer paper?
Standard printer paper is 80 GSM (metric markets) or 20 lb Bond (U.S.), which is about 75 GSM.