Thermal Conductivity Calculator — Heat Conduction Converter
Convert between thermal conductivity units including W/m·K, Btu/h·ft·°F, cal/s·cm·°C, and more. Essential for heat transfer analysis, materials engineering, and thermal design. See also our Thermal Resistance Calculator and Specific Heat Calculator.
How to Convert Thermal Conductivity
- Enter the thermal conductivity value to convert.
- Select the source unit from the dropdown.
- Click Calculate to see the value in all other units.
- Higher thermal conductivity means better heat conduction.
Thermal Conductivity Formula
Fourier's Law of Heat Conduction:
Q = -k × A × (dT/dx)
Where:
Q = Heat flow rate (W)
k = Thermal conductivity (W/m·K)
A = Cross-sectional area (m²)
dT/dx = Temperature gradient (K/m)
For steady-state conduction through a wall:
Q = k × A × ΔT / L
Where:
ΔT = Temperature difference (K)
L = Thickness (m)
Thermal resistance relationship:
R = L / (k × A)
Where R = thermal resistance (K/W)Example Calculation
Problem: Aluminum has thermal conductivity of 200 W/m·K. Convert to Btu/h·ft·°F.
Given: k = 200 W/m·K
Solution: k = 200 ÷ 1.731 = 115.5 Btu/h·ft·°F
Answer: Aluminum has thermal conductivity of 115.5 Btu/h·ft·°F.
Thermal Conductivity Reference Table
| Material | k (W/m·K) | k (Btu/h·ft·°F) |
|---|---|---|
| Silver | 429 | 248 |
| Copper | 401 | 232 |
| Aluminum | 237 | 137 |
| Steel (carbon) | 50 | 29 |
| Stainless Steel | 16 | 9.2 |
| Iron | 80 | 46 |
| Lead | 35 | 20 |
| Concrete | 1.7 | 0.98 |
| Glass | 1.0 | 0.58 |
| Water (20°C) | 0.60 | 0.35 |
| Air (20°C) | 0.026 | 0.015 |
| Fiberglass insulation | 0.04 | 0.023 |
Technical Details
Thermal conductivity is an intrinsic material property that quantifies the ability to conduct heat. It varies with temperature, pressure, and material composition. Metals generally have high thermal conductivity due to free electrons, while insulators have low values due to limited heat transfer mechanisms. The SI unit W/m·K represents watts per meter per Kelvin temperature difference. Thermal conductivity is used in Fourier's law to calculate heat transfer rates and is essential for thermal design in engineering applications including heat exchangers, building insulation, and electronic cooling.
Frequently Asked Questions
What is thermal conductivity?
Thermal conductivity measures how well a material conducts heat. It's the heat flow rate per unit area per unit temperature gradient. Higher values indicate better heat conduction.
Why do metals have high thermal conductivity?
Metals have free electrons that can move easily and transfer kinetic energy (heat) throughout the material. This electron mobility makes metals excellent thermal and electrical conductors.
How does temperature affect thermal conductivity?
For metals, thermal conductivity generally decreases with temperature due to increased electron scattering. For insulators and semiconductors, it may increase or decrease depending on the dominant heat transfer mechanism.
What's the difference between thermal conductivity and thermal diffusivity?
Thermal conductivity (k) measures steady-state heat conduction. Thermal diffusivity (α = k/ρcp) measures how quickly temperature changes propagate through a material during transient heating.
How is thermal conductivity measured?
Common methods include the guarded hot plate (steady-state), transient plane source, and laser flash techniques. Each method suits different materials and temperature ranges.