Thermal diffusivity calculator

How this calculator works

Thermal diffusivity measures how quickly a temperature disturbance spreads in a homogeneous material. Conductivity moves energy while rho cp stores it per unit volume per kelvin, so their ratio has units m²/s. Metal reference sets combine OpenStax specific heats and near-zero-Celsius conductivities with NIST nominal elemental densities. The water set uses the Concord Consortium table at 20 C. Metal sets illustrate the calculation across differing reference conditions; they are not precision matched datasets. Use custom properties for the actual state, including oils, wood, rubber and directional composites.

Formula

alpha = k/(rho cp); k = alpha rho cp; rho = k/(alpha cp).

Worked example

A custom material with k = 1 W/(m K), rho = 1000 kg/m³ and cp = 1000 J/(kg K) has alpha = 1e-6 m²/s. Doubling k to 2 gives 2e-6 m²/s.

Frequently asked questions

Sources

• OpenStax University Physics: Heat transfer, specific heat and calorimetry, Table 1.3
• OpenStax University Physics: Mechanisms of heat transfer, Table 1.5
• NIST: nominal elemental densities, Table 1
• Concord Consortium Energy2D: water thermal properties at 20 C
• NPTEL: thermal diffusivity definition