Power Derating with Temperature

Calculate allowable power at a given ambient temperature using a standard derating curve (typically linear).

How to Use

  1. Enter the rated power at the reference temperature (often 25°C or 70°C).
  2. Set the reference temperature and maximum temperature from the datasheet derating curve.
  3. Enter your ambient temperature.
  4. Review allowable power, percent derate, and margin.
Derating Curve View
Visual feedback: allowable power drops as ambient temperature rises.
P Rated
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T Ref
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T Amb
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P Allow
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Status: —
Temperature (°C) Allowable Power Tref Tmax Tamb Typical linear derating: full power until Tref, then linearly to 0 at Tmax.
Inputs & Settings
Enter datasheet points. Tool computes allowable power at ambient temperature.
Example: 0.25W, 0.5W, 1W, 2W
Common reference: 25°C or 70°C (per datasheet)
Often a “zero power” point on derating curve
Your expected ambient (or case/board temp if that’s what the curve uses)
Quick Adjust
25 °C

Tip: Sliders are for quick “what-if” checks. Use the unit dropdowns for °F/°C conversions.

Show Work (step-by-step)
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Work is shown in base units (W, °C) for clarity and consistency.

Derating Reference

A common datasheet model is: Pallow = Prated at or below Tref, then linearly decreases to 0 at Tmax.

  • Below Tref: Pallow = Prated
  • Between Tref and Tmax: Pallow = Prated × (Tmax − Tamb) / (Tmax − Tref)
  • At/above Tmax: Pallow = 0
Always match the temperature definition to the datasheet curve (ambient vs case vs board).

FAQ

What temperature should I use (ambient, case, junction)?

Use the same temperature type that the derating curve is based on. Some parts derate vs ambient; others vs case or board temperature.

Why is derating often linear?

It’s a simple, conservative approximation used in datasheets and design checks. Real thermal behavior can be non-linear.

What does “Clamp below 0W” do?

It prevents negative allowable power when Tamb is above Tmax (it clamps to 0W).

Tool Info

Last updated:

Updates may include UI improvements, expanded unit support, and edge-case handling.