How this calculator works
A single sheet is far too thin to measure with a ruler, so the practical method is to measure a stack and divide. The catch is that the stack compresses under its own weight and holds air between the sheets, so a thick stack reads slightly less per sheet than a thin one. Squaring the stack and measuring near the middle gives the most even result, and a stack of a full ream of 500 sheets is the usual laboratory sample. Caliper, the paper industry term for thickness, is normally quoted in micrometres or in thousandths of an inch, which is why the default display unit here is the millimetre with four decimal places.
Formula
thickness of one sheet = stack thickness / sheets. Height of a stack = thickness of one sheet x sheets. Sheets in a stack = stack thickness / thickness of one sheet.
Worked example
A ream of 500 sheets measures 5.0 cm, so one sheet is 50 mm / 500 = 0.1 mm, or 100 micrometres. At 0.1 mm per sheet, a 2.5 cm stack holds 25 mm / 0.1 mm = 250 sheets.
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Frequently asked questions
Why does the same paper give a different thickness in different stacks?
Paper is compressible and the surface is not perfectly flat. A taller stack squeezes out air and reads thinner per sheet, so compare measurements from similar stack heights rather than mixing a 20 sheet sample with a ream.
What is caliper?
Caliper is the paper industry word for thickness, measured under a defined pressure between two flat platens. Published caliper figures assume that standard pressure, which a ruler on a kitchen table cannot reproduce.
How thick is ordinary office paper?
A typical 80 g/m2 copy paper sheet is about 0.1 mm thick, roughly 100 micrometres or 4 thousandths of an inch. Glossy and card stocks are thicker at the same weight because they are calendered differently.
Does this account for the glue on a notepad?
No. Measure loose sheets, not a padded or glued block, because the binding adds height that is not paper.