This standard specifies a method for determining the thickness of paper and paperboard based on the mechanical contact measurement principle. The core requirement involves using a dedicated thickness tester, where the sample is placed between two parallel circular measuring surfaces, and a specified constant pressure is applied (e.g., typically 100 ± 10 kPa for paper). The distance between the two measuring surfaces at this point represents the thickness to be measured. To achieve this, a thickness tester compliant with the standard (also known as a paper thickness tester or thickness gauge) must be used. Key parameters of such instruments include a specific contact pressure (e.g., 100 kPa) and a standardized measuring area (e.g., 200 mm²). This method provides a foundation for evaluating the uniformity, density, and calculation of other physical properties of paper.