Enter the junction temperature and ambient temperature into the calculator to determine the thermal resistance of the heat sink; this calculator can also evaluate any of the variables given the others are known.

## Heat Sink Thermal Resistance Formula

The following formula is used to calculate the thermal resistance of a heat sink:

R = (T_j - T_a) / P

Variables:

• R is the thermal resistance of the heat sink
• T_j is the junction temperature of the heat source
• T_a is the ambient temperature
• P is the power dissipated by the heat source

To calculate the thermal resistance of a heat sink, subtract the ambient temperature from the junction temperature of the heat source. Divide the result by the power dissipated by the heat source.

## What is a Heat Sink Thermal Resistance?

Heat Sink Thermal Resistance is a measure of a heat sink’s ability to dissipate heat. It is a crucial parameter in the design and selection of heat sinks for electronic devices, as it directly impacts the device’s operating temperature and, consequently, its performance and reliability. The thermal resistance of a heat sink is typically expressed in degrees Celsius per watt (°C/W) and is determined by the heat sink’s material, size, shape, and surface finish, as well as the airflow around it.

A lower thermal resistance indicates a more efficient heat sink, as it means that the heat sink can dissipate more heat for a given temperature rise. Conversely, a higher thermal resistance means that the heat sink is less efficient at dissipating heat, resulting in a higher operating temperature for the device.