The unit of thermal conductivity is:

The rate of heat flow is given by: $\frac{dQ}{dt}=\frac{kA\Delta T}{L}$ $
$k=\frac{(dQ/dt)\times L}{A\times \Delta T}$$Unitof$ k = \frac{\text{Watt} \times \text{m}}{\text{m}^2 \times \text{Kelvin}} = \text{W m}^{-1} \text{ K}^{-1}$.(Note:$ \text{Watt} = \text{J/s}$,soitcanalsobe$ \text{J s}^{-1} \text{ m}^{-1} \text{ K}^{-1}$).