mW/(m·K)

milliwatt per meter-kelvin

Thermal conductivityexact by definition

The milliwatt per meter-kelvin is 10⁻³ W/(m·K), the natural unit for insulating materials and gases. Still air is 26 mW/(m·K), polyurethane foam 22, aerogel 13, and argon fill in a window unit 17.

Watch out: Insulation sales literature often quotes conductivity in mW/(m·K) and thickness in millimetres precisely because the numbers look bigger. The physics is identical to the W/(m·K) figure divided by a thousand.

1 mW/(m·K) 0.001 W/(m·K)