Voltage Regulator Heat Sink Calculator

Calculate linear regulator power dissipation, junction temperature, required heatsink thermal resistance and safe output current for 7805, LM317, LDO and other voltage regulators.

⚡ Maker Rule: A linear regulator turns voltage drop into heat. If (Vin − Vout) × current is high, the regulator may overheat even at small load current. Use this with future MOSFET Power Loss Calculator, future ADC Resolution Calculator, Battery Life Calculator and Arduino ADC Calculator.

🌡️ Linear Regulator Heat Path — Vin → Vout + Heat

Input Voltage Vin

Output Voltage Vout

Load Current

Ambient Temperature

Max Junction Temperature

Regulator Package

Junction-to-Case θJC

Case-to-Sink θCS

No-Heatsink θJA Optional

For a linear regulator: power loss = (Vin − Vout) × load current. This heat must escape through the package and heatsink.

Presets:7805 12V→5VLM317 24V→12VLDO 5V→3.3V

Power Dissipation

Heatsink θSA

θJC

θCS

Ambient Temperature

Max Junction Temperature

Use this tab when you already know power loss and want to check a selected heatsink.

Input Voltage Vin

Output Voltage Vout

Total Thermal Resistance

Ambient Temperature

Max Junction Temperature

Design Margin

This estimates the maximum safe load current for a given regulator thermal path.

📐 Formula Reference

Regulator Power Loss

P = (Vin − Vout) × Iload

Temperature Rise

ΔT = P × thermal resistance

Required θSA

θSA ≤ (Tjmax − Tamb) / P − θJC − θCS

Junction Temperature

Tj = Tamb + P × (θJC + θCS + θSA)

📋 Quick Reference

Linear Regulator Heat

12V to 5V at 0.5A3.5W

9V to 5V at 0.2A0.8W

5V to 3.3V at 0.5A0.85W

Common Fixes

Reduce Vinless heat

Use buck converterefficient

Add heatsinkcooler

Watch Out

High ambienthotter

Small SMD packagelimited

No airflowderate

📚 Engineering Notes

Voltage drop becomes heatLinear regulators are simple but inefficient when Vin is much higher than Vout.

Heatsink °C/W should be lowerA lower heatsink thermal resistance means better cooling. For example, 10°C/W cools better than 25°C/W.

Use a buck converter for high currentIf power loss is several watts, a switching buck converter may be much more practical than a linear regulator.

Check the rest of the designUse future MOSFET Power Loss Calculator, future Buck Converter Inductor Calculator and Battery Life Calculator.

What is a Voltage Regulator Heat Sink Calculator?

A voltage regulator heat sink calculator estimates how hot a linear regulator will get and what heatsink thermal resistance is required to keep the junction temperature within a safe limit.

How regulator power dissipation is calculated

For a linear regulator, power loss is calculated as the voltage drop across the regulator multiplied by load current. For example, a 12V to 5V regulator at 0.5A dissipates 3.5W as heat.

When a heatsink is needed

A heatsink may be needed when the regulator power loss is high, ambient temperature is high, the package is small, or the calculated junction temperature is above the device limit.

Important limitation

This calculator is a planning aid. Final thermal design should use the regulator datasheet, PCB copper area, airflow, enclosure temperature, package thermal resistance, safe operating area and measured temperature testing.

❓ Frequently Asked Questions

A 7805 is a linear regulator. It converts the extra voltage into heat. Higher input voltage and higher load current create more heat.

°C/W means degrees Celsius rise per watt of heat. Lower °C/W means better cooling.

For low current, a linear regulator may be fine. For higher current or large voltage drop, a buck converter is usually more efficient and runs cooler.