What Is Board caliper (point and GSM)?
Updated · Vorex Packaging
Board caliper is the thickness of paperboard, usually stated in points in North America, where one point equals one thousandth of an inch. GSM, grams per square meter, measures weight rather than thickness. Both describe how sturdy a paperboard box will feel, and suppliers may quote either one.
Two boards with the same GSM can differ in thickness, because density varies by board type. That is why North American carton makers usually specify caliper in points (pt), while many international suppliers specify GSM.
How to read the numbers
- Points: an 18 pt board is 0.018 inch thick. Higher points mean thicker board.
- GSM: higher GSM means a heavier sheet, which is usually stiffer too.
- Corrugated board is described by flute and strength ratings, such as ECT, not by points.
Choosing a thickness
Thicker board feels more premium and supports heavier products, but adds weight and can make small boxes harder to fold neatly. Thin board suits light items such as cosmetics and sachets. Tell your supplier the product weight and size, and ask for a sample of the suggested board so you can feel the difference before production.
