Thermal conductivity converter
Convert between W/m·K and the imperial forms, and watch heat cross a wall made of your material.
That's about the same as glass. Through a 10 cm slab with 20 °C across it, that carries about 200 W per square meter.
What it means
How fast does heat cross?
Values are at room temperature. Conductivity changes with temperature, moisture and, for insulation, with age.
Every unit
Your conductivity in every unit
Learn
Three things worth knowing
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Insulation is trapped air
Foam, wool and feathers all score near 0.03, close to still air. They work by stopping the air from moving, not by being special.
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Fourier’s law
Joseph Fourier published the law of heat conduction in 1822, and invented the mathematical series that carries his name in order to solve it.
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k is not R
Conductivity is a property of the material; R-value belongs to a specific thickness. Doubling the thickness doubles the R-value while k stays the same.
Shortcuts
Popular conductivity conversions
Background
About thermal conductivity
Thermal conductivity, the symbol k or λ, says how readily a material passes heat: watts through one meter of thickness, per square meter, per kelvin of difference.
Copper is around 400, water 0.6, and still air 0.026, which is why every insulator is really just a way of trapping air.