Here's why:

* Thermal resistance is the opposition to the flow of heat. It's a measure of how well a material or object resists the transfer of heat energy.

* Heat flow is measured in watts (W), which represents the rate of energy transfer.

* Temperature difference is measured in Kelvin (K) or degrees Celsius (°C).

Therefore, thermal resistance is calculated as the temperature difference across a material divided by the heat flow through it.

Equation:

Thermal Resistance (R) = Temperature Difference (ΔT) / Heat Flow (Q)

Units:

R = K/W or °C/W

Note: The units of thermal resistance are sometimes expressed as °F/BTU/h, where BTU/h stands for British thermal units per hour. This unit is used primarily in the United States.