If you have ever bought paper for a printer or a business card, you have met the terms gsm, lb, caliper, and maybe even micron. These units describe paper, but they measure different things.
GSM: Grams per Square Metre
GSM (g/m²) is the metric standard. It measures the mass of one square metre of paper. Office paper: 80 gsm. Business card: 300 gsm.
LB: Pounds per Ream
The US and UK use lb (pounds per ream of 500 sheets). 20 lb US and 80 gsm describe roughly the same paper.
Caliper: Thickness in Microns
Caliper is measured in microns (µm). 80 gsm paper is typically 100–110 µm thick.
Common GSM Values
| GSM | Common Use |
|---|---|
| 35–50 gsm | Newspaper |
| 60–75 gsm | Cheaper books |
| 80–90 gsm | Office paper |
| 100–130 gsm | Brochures, flyers |
| 150–200 gsm | Posters |
| 250–350 gsm | Business cards |
| 350–450 gsm | Premium cards, packaging |
Choosing the Right Weight
- Everyday printing — 80 gsm
- Newsletters — 100–130 gsm
- Posters — 150–200 gsm
- Business cards — 300–400 gsm
Why Weight Matters for Folding
Light paper (under 100 gsm) folds easily. Mid-weight (100–200 gsm) needs a light score line. Heavy (over 250 gsm) needs a proper score to prevent cracking.
Conversion Table
| GSM | Approx. lb (Text) | Approx. lb (Cover) |
|---|---|---|
| 60 gsm | 16 lb | — |
| 80 gsm | 20 lb | — |
| 100 gsm | 24 lb | — |
| 250 gsm | — | 90 lb |
| 300 gsm | — | 110 lb |
Frequently Asked Questions
What does 80 gsm mean?
80 grams per square metre — the mass of one square metre of the paper.
Is 80 gsm thick enough for printing?
Yes, for everyday office printing.
What is the difference between gsm and lb?
GSM is metric (mass per square metre). LB is imperial (mass per ream of 500 sheets).
How thick is 80 gsm paper?
About 100–110 microns.
What is caliper?
The thickness of a single sheet of paper.
What paper weight is best for photos?
200–300 gsm for premium photo prints.
Conclusion
Paper weight is one of the most important factors when choosing paper for a project. Understanding the differences helps you pick the right paper every time.