Thermal Resistance Converter
Convert thermal resistance between kelvins per watt (K/W, the same as °C/W), kelvins per milliwatt and degree Fahrenheit hours per BTU.
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Thermal Resistance units
Every unit below converts to every other one in the calculator. Values are relative to the base unit, the kelvin per watt (K/W).
| Unit | Symbol | System | Value |
|---|---|---|---|
| Kelvin per watt | K/W | SI | Base unit |
| Degree Fahrenheit hour per BTU | °F·h/BTU | US customary | ≈ 1.895634241 K/W |
| Kelvin per milliwatt | K/mW | SI | = 1000 K/W |
Kelvin per watt quick reference
| Kelvin per watt | Degree Fahrenheit hour per BTU |
|---|---|
| 1 K/W | = 0.52752792631 °F·h/BTU |
| 10 K/W | = 5.2752792631 °F·h/BTU |
| 100 K/W | = 52.752792631 °F·h/BTU |
| 1000 K/W | = 527.52792631 °F·h/BTU |
Among the 3 thermal resistance units on this page, the smallest is the kelvin per watt (K/W) and the largest is the kelvin per milliwatt (K/mW).
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About thermal resistance units
Thermal resistance describes how strongly a particular part, such as a heat sink, a chip package or a whole wall, resists heat flow: the temperature difference needed to drive one watt through it. Its SI unit is the kelvin per watt (K/W), identical to °C/W.
It is not the same as insulance (R-value), which is per unit area (m²·K/W), or thermal conductivity, which is a property of a material (W/(m·K)). For a flat layer, thermal resistance = thickness ÷ (conductivity × area). One °F·h/BTU is about 1.8956 K/W.
Frequently asked questions
- How do I use a heat sink rating in °C/W?
- Multiply it by the heat flowing through it. A heat sink rated 2 °C/W that carries 25 W has a temperature rise of about 50 °C across it.
- Is K/W the same as °C/W?
- Yes. A kelvin and a degree Celsius have the same size, so the two units are equal.
- Is thermal resistance the same as R-value?
- No. An R-value is per unit area. Divide it by the area to get thermal resistance: a 10 m² wall with an R-value of 2 m²·K/W has a thermal resistance of 0.2 K/W.
- How many degree Fahrenheit hours per BTU are in one kelvin per watt?
- One kelvin per watt = 0.52752792631 °F·h/BTU (degree Fahrenheit hours per BTU).