In heat transfer analysis, thermal diffusivity is the thermal conductivity divided by density and specific heat capacity at constant pressure.[1] It measures the rate of transfer of heat of a material from the hot end to the cold end. It has the SI derived unit of m²/s. Thermal diffusivity is usually denoted α but a,h,κ,[2] K,[3] and D are also used. The formula is:



Together, can be considered the volumetric heat capacity (J/(m³·K)).

As seen in the heat equation,[5]