Use this electronics calculation for a first-pass component, converter, signal, motor, or sensor estimate when the stated operating conditions and units match the device data.

Junction temperature (°C)

Required number input.

Ambient temperature (°C)

Required number input.

Power dissipation (W)

Required number input.

Derive the junction-to-ambient thermal resistance from a steady-state temperature rise over dissipated power. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Thermal resistance (°C/W)

The resulting thermal resistance returned as a number.

• Thermal-resistance arithmetic assumes the stated heat path, steady state, reference temperatures, and approximately linear properties. Interface materials, airflow, orientation, spreading resistance, transient thermal impedance, nearby heat sources, mounting torque, and enclosure temperature can dominate junction temperature.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check the result against the current datasheet and worst-case operating corners, then verify the circuit or measurement with simulation and bench testing where failure matters.

• Power Dissipation from Temperature Rise

  Infer steady-state power dissipation as (Tj−Ta)/θJA from a measured junction and ambient temperature. Use the effective thermal resistance for the same assembly and cooling conditions.

• Heatsink Junction To Case Resistance

  Calculate junction-to-case thermal resistance from junction and case temperatures under steady dissipated power; junction temperature must be no lower than case temperature.

• Junction Temperature

  Estimate the semiconductor junction temperature from ambient temperature, dissipated power and thermal resistance.