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Thermal Resistance Converter

Convert thermal resistance units including K/W, °C/W, K/kW and °F·h/BTU for heat transfer and heat sink calculations.

What this tool does

Convert thermal resistance units including K/W, °C/W, K/kW and °F·h/BTU for heat transfer and heat sink calculations. Type an amount in kelvins per watt, choose the units, and the tool converts it to degree Fahrenheit hours per BTU (International Table). It offers 5 thermal resistance units and also shows the same amount in the others.

Inputs

  • Value: A number.
  • From: Choose one: Kelvin per watt, Degree Celsius per watt, Kelvin per kilowatt, Degree Fahrenheit hour per BTU (International Table), Degree Fahrenheit hour per BTU (thermochemical). Starts as Kelvin per watt.
  • To: Choose one of the same 5 units as "From". Starts as Degree Fahrenheit hour per BTU (International Table).

How to use

  1. Enter the amount you want to convert.
  2. Choose the unit to convert from and the unit to convert to.
  3. Read the result: the converted amount and the same amount in the other units. It appears once every required field has a valid value.

Worked examples

Conversions from kelvins per watt to degree Fahrenheit hours per BTU (International Table):

  • 1 K/W = 0.52752792631 °F·h/BTU (IT)
  • 5 K/W = 2.63763963155 °F·h/BTU (IT)
  • 10 K/W = 5.2752792631 °F·h/BTU (IT)
  • 50 K/W = 26.3763963155 °F·h/BTU (IT)
  • 100 K/W = 52.752792631 °F·h/BTU (IT)

Multiply the number of kelvins per watt by 0.52752792631 to get degree Fahrenheit hours per BTU (International Table). Both units are exact definitions, so 0.52752792631 is the exact factor: 1 K/W = 0.52752792631 °F·h/BTU (IT).

Sources: Kelvin per watt: SI Brochure, 9th edition (2019). Degree Fahrenheit hour per BTU (International Table): NIST SP 811 (2008), Appendix B.9.

Limitations

  • Converts the unit of a thermal resistance only. It does not calculate heat flow or temperature rise.
  • R-values (resistance per unit area) are a different quantity and are not included here.

FAQs

Q: Is K/W the same as °C/W?
A: Yes. A temperature difference of one kelvin is the same as one degree Celsius, so the two units are equal.
Q: How many °F·h/BTU is one K/W?
A: About 0.5275 °F·h/BTU, using the International Table BTU.
Q: Which BTU is used?
A: Both the International Table (IT) and the thermochemical (th) BTU are listed and labelled. The IT BTU is the default. The two differ by less than 0.1 percent.
Q: Does this convert R-values?
A: No. R-values are thermal resistance for a unit area (m²·K/W or ft²·°F·h/BTU), a different quantity from the resistance of a whole part.

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