Heat converters
Thermal Resistance Converter
Convert K/W, °F·h/BTU and the reciprocal thermal conductance units.
Result
0.527528 °F·h/BTU
1 K/W = 0.527528 °F·h/BTU
Thermal conductance is the reciprocal of thermal resistance, so those units convert through 1 ÷ value and a zero entry shows a dash.
All units for this value
| Unit | Symbol | Value |
|---|---|---|
| Kelvin per watt | K/W | 1 |
| Degree Celsius per watt | °C/W | 1 |
| Kelvin per kilowatt | K/kW | 1000 |
| Kelvin per milliwatt | K/mW | 0.001 |
| Degree Celsius hour per kilocalorie (IT) | °C·h/kcal | 1.163 |
| Degree Fahrenheit hour per BTU (IT) | °F·h/BTU | 0.527528 |
| Degree Fahrenheit second per BTU (IT) | °F·s/BTU | 1899.1 |
| Watt per kelvin (conductance) | W/K | 1 |
| BTU per hour per degree Fahrenheit | BTU/(h·°F) | 1.89563 |
About this calculator
Thermal resistance measures how strongly a material or assembly resists the flow of heat for a given amount of power, commonly used for heat sinks, insulation, and building components. This converter switches between kelvin per watt, Fahrenheit-hour per BTU, and the reciprocal conductance units used in electronics and HVAC datasheets.
How it works in plain English
Thermal resistance in kelvin per watt tells you how many degrees of temperature difference build up across an object for every watt of heat flowing through it: a heat sink rated at 2 K/W will run 2 degrees hotter than its surroundings for every watt it dissipates. The converter treats kelvin per watt as its common anchor, scaling other resistance units up or down by their equivalent factor, and separately adjusting for the size of the degree used, since a Fahrenheit degree is smaller than a kelvin.
Some datasheets instead quote thermal conductance, in watts per kelvin, which describes the opposite idea: how much heat flows through for each degree of temperature difference, so a bigger number now means better heat flow rather than worse. Conductance is the mathematical reciprocal of resistance, so the converter divides one into the value to move between the two families. Because of that reciprocal step, entering zero into a resistance field has no meaningful conductance equivalent, and the result for that row shows as a dash rather than a number.
Pick the resistance or conductance unit you're starting from and the one you want in the from and to menus, enter a value, and the converted figure appears immediately. A table lists the same quantity across every supported unit, a precision control adjusts the number of decimal places, and a swap button reverses the two selected units.
The formula
- value_in_target = value_in_source × (source factor to K/W) ÷ (target factor to K/W)
- 1 °F·h/BTU ≈ 1.895634 K/W
- 1 K/W = 1 °C/W
- W/K (conductance) = 1 ÷ (K/W)
- BTU/(h·°F) (conductance) = 1 ÷ (°F·h/BTU)
Worked example
Suppose a heat sink is rated at 1.5 °F·h/BTU and you want that in kelvin per watt to compare with a metric datasheet. Using the conversion factor, 1.5 × 1.895634 = 2.843 K/W. This tells you the heat sink builds up about 2.843 K of temperature difference for every watt of heat it must dissipate.
Typing 1.5 into the °F·h/BTU field with K/W selected as the target gives 2.843 K/W immediately. Checking the corresponding conductance value in the same table shows about 0.352 W/K, found by taking the reciprocal of 2.843, confirming that a lower resistance always corresponds to a higher conductance and vice versa.
Thermal resistance and conductance unit relationships
| Unit | Equal to (K/W) |
|---|---|
| 1 K/W | 1 |
| 1 °C/W | 1 |
| 1 K/kW | 0.001 |
| 1 °F·h/BTU | 1.895634 |
| 1 °F·s/BTU | 0.000527 |
| W/K (conductance) | reciprocal, dash at zero |
Standard SI and US customary definitions
Frequently asked questions
What does a lower thermal resistance value mean in practice?
A lower resistance in kelvin per watt means heat passes through the material or component more easily, so less temperature difference builds up for the same power. This is desirable for heat sinks and cooling components, where you want heat carried away quickly, but undesirable for insulation, where a higher resistance is actually the goal.
Why is there a dash instead of a number for some conductance conversions?
Conductance is the mathematical reciprocal of resistance, calculated as 1 divided by the resistance value. Dividing by zero has no defined result, so when the entered resistance is zero, the converter can't produce a meaningful conductance figure and displays a dash for that unit instead of a misleading number.
Why is 1 °F·h/BTU roughly 1.9 K/W instead of a rounder number?
The conversion combines two separate factors: the smaller size of a Fahrenheit degree compared to a kelvin, and the size of a BTU compared to a joule-based watt-hour. Multiplying those factors together produces the 1.895634 figure, which isn't a round number because the underlying US customary and metric unit definitions were never designed to align neatly.
Is thermal resistance the same thing as insulation R-value?
They're closely related concepts but not always the same units. Building R-values are typically thermal resistance per unit area, expressed in units like ft²·°F·h/BTU, while this converter handles overall thermal resistance for a whole component or path, expressed in K/W or °F·h/BTU without an area term.
Can I convert a conductance value directly into a resistance value?
Yes. Choose a conductance unit like W/K as your source and a resistance unit like K/W as your target; the converter automatically applies the reciprocal step behind the scenes. There's no need to manually invert the number first, since the tool handles the conversion in either direction from the same input field.
Related converters
Convert J/kg, kcal/kg, BTU/lb and other energy-per-mass fuel efficiency units.
Convert J/m³, BTU/ft³, kWh/m³ and other energy-per-volume units.
Convert temperature differences between kelvin, Celsius, Fahrenheit and Rankine degrees.
Convert coefficients of thermal expansion between 1/K, 1/°F, ppm/K and µin/(in·°F).