Thermal conductivity describes steady-state heat transfer through a material 1 m thick with a temperature difference of 1 K (or 1°C) across its surfaces. It relates the heat transferred per second through an area of 1 m² to that temperature gradient and is expressed in W/(m·K).

Thermal conductivity depends on material type, microstructure, filler content, and other factors. Scientific experiments and engineering design require accurate experimental measurements. Available methods differ in application, measurement range, precision, accuracy, and specimen-size requirements. Different methods may yield substantially different results for the same specimen.