The TAPPI T 411 standard specifies the caliper method for measuring the thickness of paper, Cardboard and composite plates. The standard describes in detail the steps and technical requirements for measuring the thickness of paper products using calipers, including specific guidance on instrument selection, Measuring location, number of measurements, etc. during operation. The standard is suitable for thickness testing of various paper and Cardboard products, ensuring the accuracy and conformity of measurement results. Through this method, the true thickness data of paper or Cardboard can be obtained, which is of great significance for product quality control, production process improvement and applicability evaluation of final products.