Heat Sink Calculator, Formula, Volume, Example

Heat Sink Calculator:

Enter the junction temperature, Rv and the power to be dissipated. Then press the calculate button to get the total required volume of heat sink material.

Enter Power Dissipated: W
Juntion Temperature: Deg
Max. Ambient Temperature W
Volumetric Thermal Resistance  
Heat Sink Volume: cm3

Heat Sink Calculation:

Heat sink is the device is used to increase the thermal resistance of the any power electronics device. Typically, it reduces the junction temperature. You can get the junction temperature from the device’s data sheet. Hence providing the appropriate heat sink is very important to thermally withstand of any power electronics device.

Here the junction temperature TJ in degree Celsius is equal to the summation of the ambient temperature Ta in degree Celsius and the power P(W) dissipated in watts times of the sum of  thermal resistance of device junction to case Rcase in °C/Watt and thermal resistance of device junction to air R1 and thermal resistance of device junction to air R2.

Heat sink
Heat sink

The formula can be written as,


Heat sink Volume Calculation

Let us calculate the total volume of the heat sink.

Volume of the Heat sink V(cm3) in cubic centimeter is equal to the P(W) power dissipated in watts times of the volumetric thermal resistance Rv divided by the difference between the junction temperature TJ to ambient temperature Ta,

Hence the formula will be,

V(cm3) = (P(W) x Rv) / (TJ – Ta)

Note that, the details of Tj can be retrieved from the data sheet.

Rv will be varied based on the type of cooling.


Let us calculate the required volume of the heat sink for dissipating 100 watts for the junction temperature of 100 deg and consider that your ambient temperature will be 50 deg with moderate cooling.

Apply our formula,

Volume = 100 x 80 / (100-50)

 = 160 cm3

According to your physical requirement, you can size the heat sink by any dimension.


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