# Thermal Conductivity Calculator

Created by Dominik Czernia, PhD candidate
Last updated: Aug 24, 2022

The thermal conductivity calculator uses the heat flux equation to estimate the material's conductivity with specific thermal conductivity constant. In the following article, we explain how to calculate thermal conductivity and present the thermal conductivity equation we're using in our tool.

Check the thermal expansion calculator if you're interested in other thermal properties of materials.

## What is thermal conductivity?

The thermal conductivity of a material is a measure of how well it conducts heat. The higher the thermal conductivity of a material, the better it conducts heat.

Thermal conductivity is an important property of materials used in many applications, such as insulation and heat exchangers. In insulation, the lower the material's thermal conductivity, the better it will insulate. In heat exchangers, the higher the material's thermal conductivity, the better it will conduct heat.

## Thermal conductivity equation

The conduction or heat transfer is a part of Fourier's law. Our heat flux calculator uses the following one-dimensional form of the thermal conductivity formula:

$q = -\frac{\lambda \cdot \Delta T}{\Delta x}$

where:

• $q$ - Heat flux, known as conduction or heat transfer, (W/m²);
• $\Delta T$ - The temperature difference across the material, Kelvins (K);
• $\Delta x$ - The distance between the ends of the material, meters (m); and
• $\lambda$ - Material's conductivity, (W/(m·K)).

The minus sign in the heat flux equation ensures that the heat goes from the warmer to the colder end of the material. However, you don't need to remember how to calculate thermal conductivity; our thermal conductivity calculator is all you need!

## How to use the thermal conductivity calculator

The heat flux calculator allows finding the heat transfer or conduction across a one-dimensional material. To use the tool:

1. Enter the thermal conductivity constant $\lambda$.
2. Specify the temperature difference $\Delta T$.
3. Input the distance $\Delta x$.
4. The thermal conductivity calculator has a built-in unit switcher for most of the variables. Use it according to your needs.

## How to measure thermal conductivity

You can measure the thermal conductivity of a material using a variety of methods, including:

• The guarded hot plate method - Commonly used method for measuring the thermal conductivity of solids. The sample is placed on a hot plate, and two thermocouples are used to measure the temperature gradient ($\Delta T$ in the thermal conductivity formula) across the sample.
• The hollow cylinder method - Typically used for measuring the thermal conductivity of liquids and gases. In this method, a cylindrical sample is placed inside a larger cylinder, and the temperature gradient is measured across the walls of the cylinder.
• The flash method - Used for measuring the thermal conductivity of very low-conductivity materials. In this method, a high-intensity light is flashed on one side of the sample, and the resulting temperature gradient is measured across the sample.

A significant role in determining thermal conductivity is the shape of the conducting material. Check the tetrahedron volume calculator or rectangular prism calculator to learn more about these figures.

Dominik Czernia, PhD candidate
q = -λΔT/Δx
Thermal conductivity constant (λ)
BTU/(h⋅ft⋅°F)
Temperature difference (ΔT)
°F
Distance (Δx)
ft
Heat flux (q)
W/m²
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