This International Standard (IS) specifies fundamental characteristics to be measured of an engineered nanoparticles sample to determine the size, the chemical composition and the specific surface area of nanoparticles in powder form. This IS is applied to both particles that have a covering material on the surface of a core material and that do not have it. The IS also specifies measurement methods for determining each of these characteristics. Excluded in this IS are characteristics that pertain to industrial applications of nanoparticles in powder form and detailed measurement protocols as well as characteristics related to health, safety, and environmental issues.