Paper Thickness Calculator (caliper & stack height from gsm)

Understanding the paper thickness calculator — concept and principle

This calculator works out the thickness of a sheet of paper from its grammage (g/m²) and density, and the height and weight of a stack. Printers, publishers and designers use it to estimate the spine width of a book, the height of a ream or whether a stack fits a tray.

Weight ÷ density = thickness: with the default inputs the result is 25 mm stack (0.1 mm per sheet).

How it is calculated

Thickness (µm) = grammage (g/m²) ÷ apparent density (g/cm³).
Stack height = thickness × number of sheets.
Sheets per cm = 10,000 ÷ thickness (µm); a 500-sheet ream = thickness × 0.5 mm.
Bulk (cm³/g) = 1 ÷ density.
Weight of the stack as A4 = grammage × 0.0624 m² × sheets ÷ 1,000 kg (A4 = 210 × 297 mm).

The principle

Grammage is mass per area and density is mass per volume, so dividing one by the other leaves a length: the thickness. With grammage in g/m² and density in g/cm³, the result comes out directly in micrometres. Papers of the same grammage can differ in thickness: bulky book papers have low density and feel thick, while coated or calendered papers are dense and thin. Bulk, the inverse of density, is the figure printers use for this.

Worked example

Default inputs: 80 g/m², density 0.8 g/cm³, 250 sheets.

Thickness = 80 ÷ 0.8 = 100 µm = 0.1 mm.
Stack = 100 × 250 ÷ 1,000 = 25 mm.
Sheets per cm = 10,000 ÷ 100 = 100; a 500-sheet ream = 50 mm.
Bulk = 1 ÷ 0.8 = 1.25 cm³/g.
Weight of 250 A4 sheets = 80 × 0.06237 × 250 ÷ 1,000 = 1.247 kg.

Each point is the calculator re-run with only “Apparent density (g/cm³)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Apparent density (g/cm³)	Sheet thickness (µm)
0.2	400
0.4	200
0.6	133
0.8	100
1	80
1.2	67
1.6	50

How to read the result

For book spines, multiply the thickness by the number of leaves (pages ÷ 2) and add the cover. Office paper of 80 g/m² is typically about 0.1 mm thick, but always check the supplier's caliper figure, because density varies with paper type.

Common mistakes

Counting pages instead of sheets (one sheet = two pages).
Assuming all 80 g/m² papers are equally thick.
Mixing µm and mm.
Forgetting coatings and cover boards in spine calculations.

Keep in mind: The density default is an example. Use the manufacturer's caliper or bulk value for production work.

Frequently asked questions

How thick is 80 gsm paper?

About 0.1 mm at a density of 0.8 g/cm³.

How tall is a ream of 500 sheets?

About 50 mm for 100 µm paper.

How do I calculate a book's spine width?

Multiply the sheet thickness by the number of leaves (pages ÷ 2) and add the cover thickness.

Sources: ISO 534, Paper and board — Determination of thickness, density and specific volume · ISO 216 (A4 = 210 × 297 mm)

Checked 9 Nov 2026. Definition of apparent sheet density (density = grammage ÷ thickness; bulk = 1 ÷ density) as used in paper testing standards (standard definition); A4 = 210 × 297 mm (ISO 216, standard value). The density default is an example value.

Your numbers