Paper Thickness Calculator
Measure a stack of paper sheets, enter the total height and sheet count, and this calculator divides it out to give you the thickness of a single sheet in millimetres, inches, microns, and caliper points (pt). Flip the mode to find how tall a stack of N sheets will be given a known thickness, or use the GSM mode to estimate thickness from paper weight and type.
How to measure paper thickness with a ruler
A single sheet of printer paper is typically only 0.08 to 0.11 mm thick - far too thin to measure reliably with an ordinary ruler. The trick is to stack many sheets together and measure the stack. Take 100 sheets from the same pack, press them firmly together on a flat surface, measure the total height, and divide by 100. The result is accurate to within a few micrometres for most purposes. For production printing, use a precision micrometer or caliper gauge instead of a ruler.
Caliper points, mm, microns and inches explained
Paper thickness is described in four units depending on context. Millimetres (mm) are the everyday metric unit. Microns (um, also written micrometer) equal one-thousandth of a millimetre and appear in technical data sheets. Decimal inches are used in North American commercial printing. Caliper points (pt) are the most common unit in the print industry: one point equals exactly 0.001 inch, so a 4 pt paper is 0.004 inches or about 0.10 mm. Most paper spec sheets list both mm and pt. Standard copy paper runs around 4 pt (0.10 mm), light cardstock around 10 pt (0.25 mm).
What is GSM and how does it relate to thickness?
GSM stands for grams per square metre. It measures how heavy a sheet is per unit area, not how thick it is. Two papers at 100 GSM can have different thicknesses if one is more densely compressed (calendered) or coated than the other. That said, GSM and thickness are correlated within each paper grade. The relationship is captured by a "bulk factor" specific to each paper type: for uncoated offset paper the bulk factor is roughly 1.20 microns per g/m2, meaning a 100 GSM uncoated sheet is approximately 120 microns (0.12 mm) thick. Gloss-coated paper is compressed more and has a lower bulk factor of around 0.82, so the same 100 GSM gloss sheet is only about 82 microns (0.082 mm). The GSM mode in this calculator uses these industry-average bulk factors to give an estimated thickness.
Pages per inch (PPI) for book and magazine binding
Book binders use pages per inch (PPI) to calculate the spine width of a bound book. PPI is simply 1 inch divided by the single-sheet thickness in inches. A typical 80 GSM uncoated text sheet at about 0.10 mm (4 pt) gives a PPI of roughly 250, meaning a 500-page book has a spine of about 2 inches. Heavier text papers lower the PPI and thicken the spine; lighter papers raise it and thin the spine. Publishers specify paper partly on PPI because spine width directly affects cover design and shelf presence.
Common paper types: typical GSM, caliper and uses
| Paper type | Typical GSM | Approx. thickness (mm) | Caliper (pt) | Common uses |
|---|---|---|---|---|
| Tissue / onionskin | 35-60 | 0.04-0.07 | 1.5-2.8 | Gift wrap, bible pages |
| Standard copy paper | 75-90 | 0.08-0.11 | 3.1-4.3 | Office printing, everyday documents |
| Premium letter paper | 90-120 | 0.10-0.14 | 4.0-5.5 | Letterhead, quality correspondence |
| Lightweight brochure | 120-150 | 0.12-0.18 | 4.7-7.1 | Inserts, leaflets |
| Text weight | 150-170 | 0.17-0.20 | 6.7-7.9 | Magazines, book pages |
| Light cardstock | 170-250 | 0.20-0.30 | 7.9-11.8 | Business cards, postcards |
| Heavy cardstock | 250-350 | 0.30-0.45 | 11.8-17.7 | Greeting cards, folders |
| Paperboard | 350-600 | 0.45-0.80 | 17.7-31.5 | Packaging, book covers |
Caliper values are industry averages. Actual thickness varies by manufacturer, coating, and calendering.
Frequently asked questions
How thick is standard office printer paper?
Most 75-80 GSM copy paper is between 0.08 and 0.11 mm thick (3.1 to 4.3 caliper points). A ream of 500 sheets is typically 50-55 mm tall, which you can measure directly and divide by 500 to get the per-sheet thickness.
What is a caliper point in paper measurement?
One caliper point (pt) equals 0.001 inch, or approximately 0.0254 mm. Paper spec sheets and printers in North America use points because the numbers are easy to work with: standard copy paper is about 4 pt, light cardstock about 10 pt, and heavy cover stock 12-16 pt.
Why measure a stack instead of a single sheet?
A single sheet of ordinary paper is only 0.1 mm thick - impossible to measure accurately with a ruler whose smallest division is 1 mm. Stacking 100 sheets gives a 10 mm stack that is easy to measure. Any small reading error affects each sheet by only 1/100 of the error, making the result about 100 times more accurate than a single-sheet attempt.
Does GSM tell you how thick the paper is?
Not exactly. GSM measures weight per unit area, not physical thickness. Two papers at identical GSM can have noticeably different thicknesses depending on the fiber type, how much the sheet is compressed (calendering), and whether it has a surface coating. Use the GSM mode here for a quick estimate, but request the actual caliper from your paper supplier for production work.
How thick does paper need to be before it needs scoring before folding?
As a rule of thumb, paper thicker than about 0.25-0.30 mm (10-12 pt) should be scored before folding. At that thickness the wood fibers can crack along the fold line, creating visible white marks across any printed area. All cover stocks, cardstocks and paperboards used in commercial print finishing are routinely scored first.