Paper weight
and thickness.
Grammage (g/m², often written gsm) is the weight of one square metre of paper. It measures weight, not thickness. Thickness is measured in microns (µm) and depends on the bulk of the paper: at the same weight, an uncoated paper is noticeably thicker than a gloss coated one.
Three quantities, three units
Grammage
The weight of one square metre. It is the figure paper is ordered and priced by.
Caliper
The thickness of one sheet, measured with a micrometer. 1,000 µm = 1 mm. It determines feel, stiffness and spine width.
Bulk
How much air the paper holds. It links the other two: the higher the bulk, the thicker the paper at the same weight.
Same weight, different thickness
Coated paper is pressed between calender rolls into a smooth, dense surface. Uncoated paper keeps more air between its fibres. So four papers of 100 g/m² can have completely different thicknesses:
| Paper type | Bulk (cm³/g) | Caliper at 100 g/m² |
|---|---|---|
| Gloss coated | 0.75 – 0.90 | 75 – 90 µm |
| Matt / silk coated | 0.90 – 1.10 | 90 – 110 µm |
| Uncoated offset | 1.20 – 1.35 | 120 – 135 µm |
| Bulky book paper | 1.50 – 2.00 | 150 – 200 µm |
| GC board | 1.30 – 1.50 | — |
Typical values. The exact caliper is given on each paper’s data sheet and we confirm it before production.
Where each quantity matters
Feel and stiffness → caliper. The hand senses thickness, not weight. Two 300 g/m² cards on different papers do not feel the same.
Spine width → caliper. Spine = (pages ÷ 2) × sheet caliper. Example: 200 pages on 125 µm paper = 100 sheets × 0.125 mm = 12.5 mm, plus the cover.
Opacity → weight and bulk. On light papers the text on the reverse shows through. Opacity improves with a higher grammage or a higher-bulk paper.
Postage and freight → weight. Weight of a piece = grammage × area × number of sheets. An A4 sheet of 80 g/m² weighs exactly 5 g, because A4 is 1/16 of a square metre.
Typical grammages by use
| Product | Grammage | Note |
|---|---|---|
| Inserts and leaflets | 40 – 60 g/m² | Lightweight papers with high opacity for their weight. |
| Book and magazine text pages | 70 – 115 g/m² | Uncoated for text, coated for photography. |
| Letterheads | 90 – 100 g/m² | Uncoated, suitable for office printers. |
| Leaflets and brochures | 115 – 170 g/m² | Matt or gloss coated. |
| Covers, posters, folders | 170 – 300 g/m² | From 170 g/m² upwards, folds are creased first. |
| Cards, packaging | 250 – 400 g/m² | Board. By convention, paper above 225 g/m² is called board. |
At Terzidis Print we print papers and boards from 40 to 400 g/m². If you have not decided, describe the use of the piece. See also how to choose paper.
Frequently asked questions
Is 300 g/m² always thicker than 250 g/m²?
Not necessarily. An uncoated 250 g/m² with a bulk of 1.3 is about 325 µm thick, while a gloss 300 g/m² with a bulk of 0.9 is about 270 µm. Within the same type of paper, however, a higher grammage does mean a thicker sheet.
How do I work out the weight of a printed piece?
Grammage × sheet area in m² × number of sheets. A 16-page A4 on 115 g/m²: 8 sheets × 0.0625 m² × 115 = 57 g. We can calculate it for you with the quote.
What is a micron?
One thousandth of a millimetre. An ordinary 80 g/m² office paper is about 100 µm thick, that is 0.1 mm.
Send us the specifications of your job.
Size, quantity, material and number of colours. We reply with a technical proposal and a quote.