Nowadays, particle size characterization has been widely used in many industrial process and quality control, as well as academic researches. In many applications, however, a simple size analysis assuming spherical particles is not sufficient since product properties and process parameters are often also related to particle shape. More detailed particle shape analysis is often required especially in pharmaceutical and toner industries.
The most common method to perform shape analysis of particulate samples is image analysis in which particle shape information is obtained through analysis of projected image of individual particles.

There are many parameters can be used in characterizing shape of particles. Some are direct measures and some are shape descriptors of individual particles.

The following are the common measured parameters:

	Equivalent Circular Area Diameter: the diameter of a circle with its area equals to the projected area of the particle.
	Least Bounding Circle: the smallest circle that encloses the particle.
	Least Feret Diameter: the smallest distance between 2 parallel lines that do not intersect the particle.
	Greatest Feret Diameter: the largest distance between 2 parallel lines that do not intersect the particle.
	Least Bounding Rectangle Width (Length): the maximum width (length) of the particle enclosed by a rectangle.
	Fiber Length (Width): the average of actual length (width) of fiber.

The following are the common descriptors:

Sphericity: the “circularity” of particle with the value between 0 and 1, with 1 representing a perfect circle. It is determined from measured area A and perimeter P, using the equation 4?A / P2. A perfect circle has sphericity of 1 while a very ‘spiky’ or irregular object has circularity closer to 0. Sphericity is sensitive to both overall form (like elongation) and surface roughness (like convexity).

Elongation: a measure of the length width relationship. It is defined as 1-[width/length]. Shapes symmetrical in all axes such as circles or squares have similar length and width (elongation close to 0). Needle-shaped particles have length > width (elongation closer to 1). Elongation not affected by surface roughness for a given width/length.

Convexity: a measure of the surface roughness of a particle. It is defined as convex hull perimeter/actual particle perimeter. Convex hull is defined as area enclosed by an imaginary elastic band surrounding shape. Smooth shapes have a convexity of 1 while very ‘spiky’ or irregular objects have a convexity closer to 0. Unlike elongation, convexity is a measure of surface roughness and is unaffected by aspect ratio.