This document specifies an oven-drying method for the determination of the dry matter content in paper, board, pulp and cellulosic nanomaterials in solid form, which all can be produced from virgin and /or recycled materials. It is also applicable to the determination of the dry matter content of paper and board for recycling. The procedure is applicable to paper, board, and pulp and cellulosic nanomaterials which do not contain any appreciable quantities of materials other than water that are volatile at the temperature of 105 °C ± 2 °C. It is used, for example, in the case of pulp, paper, and board and cellulosic nanomaterial samples taken for chemical and physical tests in the laboratory, when a concurrent determination of dry matter content is required. This method is not applicable to the determination of the dry matter content of slush pulp or to the determination of the saleable mass of pulp lots. NOTE 1: ISO 638-2 specifies an oven-drying method for the determination of the dry matter content of suspensions of cellulosic nanomaterials, ISO 287 specifies the determination of the moisture content of a lot of paper and board; ISO 4119 specifies the determination of stock concentration of pulps; ISO 801 (all parts) specifies the determination of the saleable mass in lots. NOTE 2: This document determines the total dry matter content of the sample, including any dissolved solids. If only the cellulosic material content free of dissolved solids is desired, dissolved solids are removed prior to measuring the dry matter content e.g. by washing or dialysis, taking care to retain all cellulosic material; in cases where the sample is filterable without loss of cellulosic solids, ISO 4119 can be used to determine the stock consistency (content of cellulosic material in solid form).