Analysis of particulate samples is done to find the particle size and distribution from a representative sample. A particle size distribution can be displayed either tabular form or graphically, and either as a cumulative distribution or as a differential distribution. To a sphere, the size is the diameter (or radius) of the sphere. To a real particle of arbitrary shape, the commonly acceptable size for 3-dimentional measurement techniques such as laser diffraction and Coulter principle is defined as the volume equivalent sphere diameter, i.e., a sphere with the same volume as the real particle; and the size for 2-dimentional measurement techniques such as image analysis is defined as the area equivalent circular diameter, i.e., a circle with the same area as the projected area of the real particle at the orientation of measurement. Because it is impractical to measure every particle in a bulk sample, especially for small particles, correct sampling, to ensure statistical representation of measured particles to the bulk sample, and correct particle dispersion, to ensure all particles are measured individually, are key steps in any particle size analysis experiment.

Industrial particles cover a broad range of sizes. For example, contaminants can cover five orders of magnitude in size, and powder products typically cover seven orders from decimeters to submicrons. There are many industries and even more processes that rely heavily on determining and controlling the particle size and size distribution of particulate materials. The size and size distribution of film additives, adhesives, pigment particles all affect their corresponding product quality. The gloss and hiding power of paints are affected by the presence of a few large particles and by the total fraction of small particles, respectively. Other examples of industrial processes affected by particle size are adhesion, catalysis, detergency, food processing, grinding, lubrication, ore flotation, road surfacing, etc.

There are many particle size and size distribution analysis technologies. The most common ones are laser diffraction for sizing particles from submicron to millimeter in size, Counter Principle for sizing and counting particles from micron to millimeter in size, and dynamic light scattering for sizing submicron and nanometer particles. Other common technologies for size analysis include sieve analysis and sedimentation.