Use the free tool below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.
What caliper means
Caliper is the thickness of a single sheet of paper, usually measured in millimetres or microns. One micron is one thousandth of a millimetre, so a sheet of 100 microns is 0.1 millimetres thick. Caliper matters wherever paper must fit a physical space: a book spine, a printer feed, an envelope, or a stack of sheets on a shelf. A paper supplier lists caliper in the specification sheet, but many papers are bought by weight alone, in GSM, and the thickness must then be estimated. That estimate comes from weight and density: a heavier sheet is thicker, and a denser sheet is thinner at the same weight.
This calculator estimates caliper from GSM and paper density, and it also works out the height of a stack of sheets. Choose the paper type for a typical density, or use a density from the supplier if you have one. The stack height helps with storage, postage and binding: 500 sheets of office paper make a ream about 50 millimetres tall, which is why a ream looks the way it does on a shelf.
How to use the calculator
- Enter the paper weight in GSM.
- Choose the paper type, which sets a typical density.
- Enter the number of sheets for the stack height.
- Read the sheet thickness in millimetres and microns, and the stack height in millimetres and inches.
A worked example
Take standard office paper at 80 GSM with a density of 0.80 grams per cubic centimetre. Dividing 80 by 800 gives 0.1 millimetres, or 100 microns, per sheet. A stack of 500 sheets is therefore 50 millimetres tall, which matches a real ream closely enough to plan shelf space. Now take a coated paper at the same 80 GSM but a density of 1.00. The same calculation gives 0.08 millimetres per sheet, so the coated stack is only 40 millimetres tall. Same weight, visibly different thickness: that is why weight alone never tells the full story.
Try a heavy card at 300 GSM with a density of 1.10. The thickness is about 0.273 millimetres per sheet, and 100 sheets stack to about 27 millimetres. That stack height matters for a box or a display stand, and the per-sheet thickness matters for a book spine, where 100 sheets of this card add nearly 30 millimetres to the text block. The spine width calculator takes the caliper number from this tool and turns it into a cover measurement.
Density by paper type
- Uncoated offset paper: about 0.75 grams per cubic centimetre, bulky and soft.
- Standard office paper: about 0.80, the everyday reference point.
- Light coated paper: about 0.90, smoother and slightly denser.
- Gloss coated paper: about 1.00, dense and smooth.
- Dense coated board: about 1.10, the stiffest common stock.
These are typical values, not guarantees. A bulky book paper can be far less dense than 0.75, and a specialty board can exceed 1.10. If the exact caliper matters for a binding or a machine feed, measure it with a micrometer or ask the supplier for the caliper specification. The micrometer reading is the truth; this calculator is the estimate you use while planning, before the paper arrives.
Measuring caliper yourself
A cheap digital micrometer measures a single sheet well enough for most planning, but paper compresses under the micrometer foot, so take several readings and average them. A more reliable home method is to measure a stack: count 100 sheets, measure the stack height with a ruler, and divide by 100. The stack method averages out the variation between sheets and the compression error, and it needs no special tool. Whatever method you use, record the paper, the GSM and the measured caliper together, because that record is what makes the next job faster. Estimating from GSM gets you close; measuring gets you exact.
Related calculators
- Spanish version
- Paper Weight Converter – GSM to US Bond, Cover and Text Weights
- DPI to PPI Converter – Print Resolution to Screen Resolution Conversion