Thermal Resistance Converter

Thermal resistance (R) is how strongly an object holds back the flow of heat: the temperature difference across it for each watt of heat passing through, R = ΔT / P. Its SI unit is the kelvin per watt (K/W), which is the same as °C/W, since a difference of 1 K equals one of 1 °C.

It is how heat sinks and chip packages are rated. A heat sink of 0.5 K/W carrying 100 W from a processor runs 100 × 0.5 = 50 °C warmer than the air around it.

How to convert thermal resistance units

Type a value into any field, and every other unit is calculated at once. For example, 0.5 K/W:

1. In °C/W: the same number.

   0.5 K/W = 0.5 °C/W

2. In °F·h/Btu: multiply by 0.527528.

   0.5 × 0.527528 = 0.2638 °F·h/Btu

Common conversions

Thermal resistance units

• Kelvin per Watt (K/W): Kelvin per Watt is the standard unit of thermal resistance in the International System of Units (SI). It represents the temperature difference of one Kelvin across a material or system per unit of heat transfer in Watts. This unit is equivalent to degree Celsius per Watt (°C/W).
  Conversion Factor: 1 K/W = 1 °C/W (Base Unit)

• Fahrenheit-hour per Btu (°F•h/Btu): This unit is commonly used in the United States and represents the temperature difference of one degree Fahrenheit sustained for one hour per unit of heat transfer in British Thermal Units.
  Conversion Factor: 1 °F•h/Btu(IT) = 1.8956 K/W; 1 °F•h/Btu(th) = 1.8969 K/W

• Fahrenheit-second per Btu (°F•s/Btu): This unit introduces time as seconds, representing the temperature difference of one degree Fahrenheit sustained for one second per unit of heat transfer in British Thermal Units.
  Conversion Factor: 1 °F•s/Btu(IT) = 0.0005265651 K/W; 1 °F•s/Btu(th) = 0.0005269175 K/W

Frequently asked questions

Is K/W the same as a building R-value?

No. K/W belongs to one whole object, such as a heat sink. A building R-value is per square meter of wall, in m²·K/W, or in h·ft²·°F/Btu in the US, where 1 m²·K/W = 5.67826 h·ft²·°F/Btu. An R-value is the inverse of a U-value, which the Heat Transfer Coefficient Converter converts.

Is K/W the same as °C/W?

Yes. A temperature difference of 1 K is the same as one of 1 °C, so the number is the same in both.