Short answer: GSM is the weight, in grams, of one square metre of a material such as paper or fabric. A higher number means a heavier material per area. It is a measure of weight, not of thickness.
What two sources say about GSM
| Source page | Publisher | What the page says |
|---|---|---|
| Grammage - Wikipedia | Wikipedia | Explains grammage as the mass of paper or paperboard per unit area, in grams per square metre, often written gsm on labels. It gives about 80 g/m2 for typical office paper and says the measure is independent of thickness. |
| GSM - Explanation, Thickness, Paper & Fabric Weight | Bachelorprint (printing guide) | Describes GSM as the weight of one square metre of paper and of fabric, and treats it as separate from thickness. For fabric it links GSM to how heavy or dense the cloth is, which affects feel and drape. |
Key points
- GSM means grams per square metre: the mass of a material divided by its area in square metres. [1, 2]
- For paper and paperboard it appears on labels and spec sheets as gsm or g/m2. [1]
- Ordinary office paper is about 80 gsm. [1]
- GSM is not the same as thickness. Thickness is a separate measure of depth. [1, 2]
- The same unit is used for fabric, where it shows how heavy or dense the cloth is. [2]
- Higher GSM usually goes with thicker material, but treating the two as equal is a common mistake. [2]
GSM compared with Caliper (thickness)
| Aspect | GSM | Caliper (thickness) | Source |
|---|---|---|---|
| What it measures | Mass per unit area, in grams per square metre. | Physical depth of the sheet. | [1, 2] |
| Typical units | g/m2 (gsm). | Microns or points. | [2] |
| Link between them | Higher GSM usually means thicker stock. | Not guaranteed to follow GSM, so the two should not be treated as equal. | [2] |
| Use for fabric | Shows how heavy or dense a fabric is, affecting feel and drape. | Not covered for fabric by these sources. | [2] |
Where sources differ
The Wikipedia page was read for paper and paperboard only and does not discuss fabric. Fabric use rests on the Bachelorprint guide alone. Bachelorprint is a student-printing service, used here as a trade guide.
Questions to ask a supplier about GSM
- [ ] What GSM is quoted, and how is it measured or checked?
- [ ] Is the GSM given for the bare material or for the finished product?
- [ ] What is the allowed tolerance on the stated GSM?
- [ ] Does the stated GSM come with a thickness figure as well?
- [ ] Is the weight measured in the same way for every batch?
Read next on this site
- Printed cushion and curtain fabrics for private label
- Fabric Furnishings Buyer Guide for Private Label
- Fabric Furnishings: 18 Products in Five Families (Data)
More terms and explainers
- Martindale test / rub count
- Mat board / mount board
- MDF
- Tempered glass
- How to Read a Product Spec Sheet Before You Approve It
Start an enquiry when your list is ready; we reply within 1 business day.
Sources: [1] Wikipedia, fetched 2026-11-12; [2] Bachelorprint (printing guide), fetched 2026-11-12. As of 2026-11-12. General information, not legal, customs or tax advice. Wording is paraphrased from the pages linked; your written quote and contract govern.