Particle size have significant impact on Ayurvedic churna dissolution as well as on drug absorption. Its role in dissolution rate is described starting from the Noyes–Whitney equation, the modified form by Nerst–Brunner and the cube root equation. According to these equations diffusion of solute (Particle Size) through a boundary layer around the particles is the rate limiting step in drug dissolution and as well as in absorption, thus, its depends upon the specific (external) surface area of the particles, the diffusion coefficient of the solute, the thickness of the boundary layer and the solute solubility. In relation to this, good wetting of the particle surface by the surrounding liquid and adequate particle dispersion play an essential role