Thermal conductivity is a fundamental material property that quantifies a substance's ability to conduct heat. In engineering, two primary systems are frequently encountered: the SI unit and the Imperial/US Customary unit.
Watt per meter-Kelvin (W/(m·K)): The SI unit representing the rate of heat transfer through a material of unit thickness and unit area under a temperature gradient of one Kelvin. It is defined as \(1 \text{ W/(m·K)} = 1 \text{ W} \cdot \text{m}^{-1} \cdot \text{K}^{-1}\).
BTU per hour-foot-Fahrenheit (BTU/(hr·ft·°F)): The Imperial unit commonly used in HVAC, building construction, and industrial insulation specifications in the United States. It represents the heat flow in British Thermal Units per hour through a one-foot thick layer of material with a one-degree Fahrenheit temperature difference.
Engineers often need to convert between these units when working with international material datasheets or legacy building codes. The conversion factor is derived from the relationships between the Joule, the BTU, the meter, the foot, and the temperature scales.
Watt per meter-Kelvin to BTU per hour-foot-Fahrenheit Conversion Reference Table
Watt per meter-Kelvin (W/(m·K))
BTU per hour-foot-Fahrenheit (BTU/(hr·ft·°F))
0.1
0.0578
0.5
0.2889
1.0
0.5778
2.0
1.1556
5.0
2.8889
10.0
5.7779
20.0
11.5558
50.0
28.8895
100.0
57.7789
500.0
288.8946
1000.0
577.7892
Conversion Example: 10 W/(m·K)
To convert a thermal conductivity value from SI to Imperial units, multiply the value by the conversion factor of approximately 0.577789.
This factor is derived from the conversion of 1 Watt (1 J/s) to BTU/hr and the conversion of meters to feet, combined with the temperature interval ratio where 1 Kelvin equals 1.8 degrees Fahrenheit.
No, they are not interchangeable. While they measure the same physical property, they belong to different measurement systems. Always verify the required unit specified in your local building code or project technical specification.
"On fait la science avec des faits, comme on fait une maison avec des pierres ; mais une accumulation de faits n'est pas plus une science qu'un tas de pierres n'est une maison." "Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house." — Henri Poincaré (French Mathematician, Theoretical Physicist & Mining Engineer)