Thermal Conductivity Converter
Convert thermal conductivity values between common SI, metric and Imperial/US customary units. Enter a value, choose the starting unit and the unit you want to convert to.
Equivalent thermal conductivity values
| Unit | Equivalent value |
|---|
What is thermal conductivity?
Thermal conductivity describes how readily heat passes through a material. A higher thermal conductivity means heat moves through the material more easily, while a lower value means the material resists heat flow more strongly.
The coherent SI unit for thermal conductivity is the watt per metre kelvin, written as W/(m·K). Because a temperature difference of 1 kelvin is the same size as a temperature difference of 1 degree Celsius, W/(m·K) and W/(m·°C) have the same numerical value when expressing thermal conductivity.
How to use the thermal conductivity converter
- Enter the thermal conductivity value you want to convert.
- Select the unit the value is currently expressed in.
- Select the unit you want to convert to.
- Press Convert to see the result and a table of equivalent values.
You can also use Swap units to reverse the selected conversion.
Thermal conductivity conversion formulas
CalcAtlas converts the entered value to the SI base used on this page, W/(m·K), and then converts that SI value to the selected output unit.
| Unit | Equivalent in W/(m·K) |
|---|---|
| 1 W/(m·K) | 1 W/(m·K) |
| 1 W/(m·°C) | 1 W/(m·K) |
| 1 mW/(m·K) | 0.001 W/(m·K) |
| 1 kW/(m·K) | 1000 W/(m·K) |
| 1 Btu/(h·ft·°F) | 1.730735 W/(m·K) |
| 1 Btu·in/(h·ft²·°F) | 0.1442279 W/(m·K) |
| 1 cal/(s·cm·°C) | 418.4 W/(m·K) |
| 1 kcal/(h·m·°C) | 1.162222222 W/(m·K) |
Btu conversions on this page use the International Table Btu (BtuIT). Calorie and kilocalorie conversions use the thermochemical calorie (1 cal = 4.184 J).
Conversion reference
The thermal conductivity conversion factors used on this page are based on published unit-conversion data from the National Institute of Standards and Technology (NIST) .
Example: convert W/(m·K) to Btu/(h·ft·°F)
Suppose a material has a thermal conductivity of 0.040 W/(m·K). Since 1 Btu/(h·ft·°F) equals approximately 1.730735 W/(m·K):
0.040 ÷ 1.730735 ≈ 0.02311 Btu/(h·ft·°F)
So 0.040 W/(m·K) is approximately 0.02311 Btu/(h·ft·°F).
Common thermal conductivity units
Engineering and scientific data commonly use W/(m·K). Milliwatts per metre kelvin are convenient for low-conductivity insulation materials, while Btu/(h·ft·°F) and Btu·in/(h·ft²·°F) are still encountered in Imperial and US customary engineering references.
Take care not to confuse thermal conductivity with thermal conductance or a heat-transfer coefficient. Their units are different, so they are not interchangeable without additional geometric or physical information.
Frequently asked questions
What is the SI unit of thermal conductivity?
The SI coherent derived unit is watt per metre kelvin, W/(m·K).
Is W/(m·K) the same as W/(m·°C)?
For thermal conductivity, yes. A kelvin and a degree Celsius represent the same size temperature interval, so the numerical conductivity value is unchanged.
How do I convert Btu/(h·ft·°F) to W/(m·K)?
Multiply the Btu/(h·ft·°F) value by approximately 1.730735 when using the International Table Btu.
How do I convert W/(m·K) to Btu/(h·ft·°F)?
Divide the W/(m·K) value by approximately 1.730735.
Can thermal conductivity be negative?
For ordinary passive materials, thermal conductivity is normally reported as a positive quantity. This converter therefore accepts values of zero or greater and rejects negative inputs.