Thermal diffusivity combines how well a material conducts heat with how much heat it stores. Metals have high diffusivity and feel cold to the touch; wood has low diffusivity and feels warm.
How to use the Thermal Diffusivity Calculator
- Material
- Thermal conductivity k
- Density ρ
- Specific heat c_p
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose a material or enter its properties.
Tips
- Use absolute temperature (K) in gas laws and efficiency formulas.
- Temperature differences are the same in K and °C.
- Heat = mass × specific heat × temperature change when no phase change occurs.
- Phase changes need latent heat at a constant temperature.
Common mistakes to avoid
- Using °C in pV = nRT.
- Forgetting latent heat during melting or boiling.
- Confusing heat capacity (J/K) with specific heat (J/(kg·K)).
Inputs explained
| Field | What to enter |
|---|---|
| Material | Choose one: Copper, Aluminium, Carbon steel, Stainless steel … |
| Thermal conductivity k | Units: W/(m·K), BTU/(h·ft·°F) |
| Density ρ | Units: kg/m³, g/cm³, g/mL, lb/ft³, lb/in³ |
| Specific heat c_p | Units: J/(kg·K), kJ/(kg·K), J/(g·K), BTU/(lb·°F), cal/(g·°C) |
What each result means
- Thermal diffusivity α = [k]÷([rho]×[cp])
- Time for heat to penetrate 1 cm (≈ L²/α) = 1e-4÷[Thermal diffusivity α]
Example values
How the main result changes when Thermal conductivity k changes and everything else stays at the example values above:
| Thermal conductivity k (W/(m·K)) | Thermal diffusivity α (mm²/s) |
|---|---|
| 0.5 | 116.2454 |
| 0.75 | 116.2454 |
| 1 | 116.2454 |
| 1.25 | 116.2454 |
| 1.5 | 116.2454 |
| 2 | 116.2454 |
Formula
α = k / (ρ·c_p)Worked example
Inputs — Material: Copper.
Results — Thermal diffusivity α = 116.24536 mm²/s; Time for heat to penetrate 1 cm (≈ L²/α) = 0.8602 s.
Key terms
- Thermal diffusivity
- Rate of temperature spreading, k/(ρc_p).
Frequently asked questions
Why does metal feel colder than wood?
Its high diffusivity draws heat from your hand quickly.
What is the diffusivity of water?
About 0.14 mm²/s.
How is it used?
In transient heat problems – cooking times, quenching, building thermal mass.
What units does it have?
m²/s, like kinematic viscosity.
What formula does the Thermal Diffusivity Calculator use?
α = k / (ρ·c_p).