Weight vs thickness

Paper weight and thickness are distinct physical properties, though they are often conflated in casual conversation. Weight, measured in grams per square metre (GSM) or pounds per ream, indicates the mass of the sheet relative to its surface area. Thickness, measured in microns or points, indicates the actual depth of the material.

Because different paper types have different densities (bulk), two sheets with the same weight can have different thicknesses. For example, a 300 GSM uncoated cardstock is typically thicker than a 300 GSM coated paper: coating compacts the sheet to a higher density, so the same mass occupies less depth.

Weight and thickness have no direct conversion — but thickness converts cleanly to other thickness units: in the US paper trade, 1 point (pt) = 0.001 in = 0.0254 mm exactly. (Beware: the typographic “point” used for font sizes is 1/72 in — a different unit.) To estimate thickness from weight you need the stock’s bulk: caliper (mm) ≈ GSM × bulk ÷ 1000. When specifying business cards, it is critical to distinguish between these metrics to ensure the card feels substantial enough for its intended use.