Calculate thickness, density, or GSM from any two values with unit conversions for mm, cm, m, in, ft, g/cm³, kg/m³, lb/ft³, and g/m².
| Thickness to GSM | GSM to Thickness |
|---|---|
| 0.05 mm = 50 g/m² | 60 g/m² = 0.0600 mm |
| 0.08 mm = 80 g/m² | 70 g/m² = 0.0700 mm |
| 0.10 mm = 100 g/m² | 75 g/m² = 0.0750 mm |
| 0.12 mm = 120 g/m² | 90 g/m² = 0.0900 mm |
| 0.15 mm = 150 g/m² | 110 g/m² = 0.1100 mm |
| 0.20 mm = 200 g/m² | 130 g/m² = 0.1300 mm |
| 0.25 mm = 250 g/m² | 160 g/m² = 0.1600 mm |
| 0.30 mm = 300 g/m² | 180 g/m² = 0.1800 mm |
| 0.40 mm = 400 g/m² | 220 g/m² = 0.2200 mm |
| 0.50 mm = 500 g/m² | 250 g/m² = 0.2500 mm |
| 0.75 mm = 750 g/m² | 350 g/m² = 0.3500 mm |
| 1.00 mm = 1000 g/m² | 600 g/m² = 0.6000 mm |
| Formulas (brief): GSM = t × ρ × 1000, and t = GSM ÷ (ρ × 1000). Table assumes ρ = 1.0 g/cm³. | |
| Thickness to GSM | GSM to Thickness |
|---|---|
| 0.05 mm = 45 g/m² | 40 g/m² = 0.0444 mm |
| 0.08 mm = 72 g/m² | 60 g/m² = 0.0667 mm |
| 0.10 mm = 90 g/m² | 80 g/m² = 0.0889 mm |
| 0.12 mm = 108 g/m² | 100 g/m² = 0.1111 mm |
| 0.15 mm = 135 g/m² | 120 g/m² = 0.1333 mm |
| 0.20 mm = 180 g/m² | 150 g/m² = 0.1667 mm |
| 0.25 mm = 225 g/m² | 200 g/m² = 0.2222 mm |
| 0.30 mm = 270 g/m² | 250 g/m² = 0.2778 mm |
| 0.40 mm = 360 g/m² | 300 g/m² = 0.3333 mm |
| 0.50 mm = 450 g/m² | 400 g/m² = 0.4444 mm |
| 0.75 mm = 675 g/m² | 500 g/m² = 0.5556 mm |
| 1.00 mm = 900 g/m² | 800 g/m² = 0.8889 mm |
| Formulas (brief): GSM = t × ρ × 1000, and t = GSM ÷ (ρ × 1000). Table assumes ρ = 0.9 g/cm³. | |
mm to GSM Formula
Thickness in millimeters and GSM are linked by the density of the material. To find GSM from a thickness, multiply the thickness in millimeters by the density in grams per cubic centimeter, then by 1000:
GSM = T * D * 1000
To go the other way and find thickness from a known GSM, divide instead:
T = GSM / (D * 1000)
To find the density that a GSM and thickness imply, rearrange again:
D = GSM / (T * 1000)
Variables:
- GSM is the area weight in grams per square meter (g/m²)
- T is the thickness in millimeters (mm)
- D is the density in grams per cubic centimeter (g/cm³)
- 1000 is the factor that converts the product into grams per square meter
Pick what you want to solve for at the top of the calculator. In the default mode you enter a thickness and a density and the tool returns the GSM. Switch the selector to solve for thickness when you know the GSM and density, or to solve for density when you know both the GSM and the thickness.
Thickness alone cannot give you GSM, because two sheets of the same thickness weigh different amounts if one is packed more densely than the other. That is why the density input is required. If you do not know the density, use the material menu to load a typical value, then adjust it if you have a better figure. The thickness, GSM, and density inputs each accept more than one unit, and every result also lists the common equivalent units so you can read the answer in whatever measure you need.
Typical Densities and Thickness to GSM Values
The density you enter drives the whole conversion. Use the first table to pick a starting density for common paper and board, then the second table to see how a given thickness turns into GSM at two common densities.
| Material | Typical density (g/cm³) |
|---|---|
| Newsprint | 0.55 to 0.60 |
| Standard copy / office paper | 0.75 to 0.80 |
| Bond / offset paper | 0.80 to 0.85 |
| Cardstock / cover stock | 0.80 to 0.90 |
| Coated / glossy paper | 1.00 to 1.20 |
| Water (reference) | 1.00 |
These values are approximate. Paper stock varies by brand and finish, so treat them as a starting point rather than an exact figure. The table below assumes a solid, uniform material.
| Thickness (mm) | GSM at 0.80 g/cm³ | GSM at 1.00 g/cm³ |
|---|---|---|
| 0.05 | 40 | 50 |
| 0.08 | 64 | 80 |
| 0.10 | 80 | 100 |
| 0.15 | 120 | 150 |
| 0.20 | 160 | 200 |
| 0.25 | 200 | 250 |
| 0.30 | 240 | 300 |
| 0.40 | 320 | 400 |
| 0.50 | 400 | 500 |
Example Problems
Example 1: Find GSM from thickness and density.
A sheet is 0.2 mm thick with a density of 0.80 g/cm³. Multiply the three terms:
GSM = 0.2 * 0.80 * 1000 = 160 g/m².
Example 2: Find thickness from GSM and density.
A card is rated at 300 g/m² and its stock has a density of 0.85 g/cm³. Divide to get the thickness:
T = 300 / (0.85 * 1000) = 0.353 mm.
Frequently Asked Questions
Can you convert mm to GSM without knowing the density?
No. GSM measures weight per square meter, and thickness measures height, so you need the density to connect the two. Two sheets can have the same thickness but different GSM if one material is packed more tightly. If you do not have a measured density, use a typical value for your material, such as about 0.80 g/cm³ for standard paper, and treat the result as an estimate.
What density should you use for paper?
Most office and copy paper sits near 0.75 to 0.80 g/cm³. Newsprint is lighter at about 0.55 to 0.60, while coated or glossy stock is denser at roughly 1.00 to 1.20. Cardstock usually falls between 0.80 and 0.90. These are approximate because finish, coating, and fiber all affect how tightly the sheet is packed, so measure the density yourself when accuracy matters.
Is GSM the same as thickness?
No. GSM is the weight of a one square meter sheet, while thickness is how tall the sheet stands, usually reported in millimeters or microns. They rise together for a single material, but you cannot swap one for the other across materials without the density. A thin, dense sheet and a thick, airy sheet can share the same GSM.
