Thermal Resistance Converter

What Is Thermal Resistance

Thermal resistance measures how much a material resists heat flow. You express this property in kelvin per watt (K/W) or degrees Celsius per watt (°C/W). Higher thermal resistance means better insulation. Lower thermal resistance means better heat conduction.

Electronics engineers use thermal resistance to design heat sinks and cooling systems. You calculate junction temperatures using thermal resistance values. Building professionals specify insulation R-values which represent thermal resistance per unit area.

Thermal Resistance Formula

Calculate thermal resistance for conduction using this formula:

Where R equals thermal resistance in K/W, d equals material thickness in meters, k equals thermal conductivity in W/(m·K), and A equals cross-sectional area in square meters.

You can also calculate thermal resistance from temperature difference and heat flow:

Where ΔT equals temperature difference in kelvin and Q equals heat flow in watts.

Example: A component generates 50 W and operates 40°C above ambient. The thermal resistance equals:

Thermal Resistance in Electronics Cooling

Electronics datasheets specify junction-to-case and junction-to-ambient thermal resistance. You use these values to calculate maximum operating temperatures.

Calculate junction temperature using: Tj = Ta + (Q × Rθj-a). Where Tj equals junction temperature, Ta equals ambient temperature, Q equals power dissipation, and Rθj-a equals junction-to-ambient thermal resistance.

R-Value for Building Insulation

R-value measures thermal resistance per unit area in building construction. You calculate total wall resistance by adding individual layer R-values.

Unit Conversion Factors

Frequently Asked Questions