thickness

Thickness is a measure of how thick an object is, defined as the distance between two parallel surfaces measured perpendicular to those surfaces. It is one of the three principal dimensions of a solid, along with length and width, and is often the smallest dimension in a component. For layered or flexible materials, thickness may vary across the area.

Thickness is usually expressed in meters, millimeters, micrometers, or nanometers, depending on scale. Practical measurement tools include calipers and micrometers for bulk parts; profilometers or optical interferometers for surface profiles; ellipsometry for very thin films; and ultrasonic or X-ray methods when the thickness is hidden or composite.

In engineering and manufacturing, thickness influences mechanical strength, stiffness, thermal and electrical insulation, wear resistance, and how parts fit together. Coatings, laminates, and protective layers are specified by thickness and tolerances. In construction, wall or slab thickness affects load capacity and thermal performance.

Thickness can be affected by processing conditions, material anisotropy, temperature, and handling. For thin films, uniformity is crucial and measured at micro- to nanometer scales; for bulk parts, tolerances reflect functional requirements and production capabilities.

Standards organizations such as ISO and ASTM publish methods and tolerance guidelines for thickness measurement across materials and applications.

See also: thickness measurement, film thickness, coating thickness, gauge, caliper, profilometry.