Thermal - Heatsink - Required Rth Calculator

https://www.heatsinkcalculator.com/heat-sink-thermal-resistance-calculator.html

This calculator lets you input LED and TIM parameters and solves for the heatsink Rth needed to achieve the Tj input.  The label is Tj(max) but you can set it at any value you want, such as 85 C, and solve for the Rth you need to operate at your target Tj. 

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