Our thermal resistance converter allows precise conversion between different units of resistance to heat flow, including kelvin per watt, celsius per watt, and fahrenheit hour per BTU.
Thermal resistance is a measure of a material or system's ability to resist heat flow. It is the reciprocal of thermal conductance and represents the temperature difference needed to transfer a unit of heat power through a material or interface. In building science, thermal resistance is commonly known as the R-value, with higher values indicating better insulation performance.
Convert between different thermal resistance units with our free online calculator. Perfect for engineering, scientific, and professional applications.
Common thermal resistance conversions
| From | To | Context |
|---|---|---|
| 1 Kelvin Per Watt (K/W) | 0.5250 Fahrenheit Hour Per Btu (°F·h/BTU) | Standard conversion factor |
| 19 Fahrenheit Hour Per Btu (°F·h/BTU) | 36.1900 Kelvin Per Watt (K/W) | R-19 insulation (US standard) |
| 0.5 Celsius Per Watt (°C/W) | 0.5000 Kelvin Per Watt (K/W) | Electronic component thermal resistance |
Thermal resistance (R-value) is used to specify insulation requirements and evaluate building envelope performance for energy efficiency.
In electronic design, thermal resistance values help engineers select appropriate cooling solutions for components like CPUs and power transistors.
Thermal resistance calculations are essential for sizing heating and cooling equipment based on building heat loss and gain.
Higher thermal resistance in building components reduces energy consumption for heating and cooling, improving overall energy efficiency.
R-value measures thermal resistance (how well a material resists heat flow), with higher values indicating better insulation. U-value measures thermal transmittance (how easily heat flows through a material), with lower values indicating better insulation. They are reciprocals of each other: U = 1/R.
For a homogeneous material, thermal resistance (R) increases linearly with thickness (d) according to the formula: R = d/k, where k is the thermal conductivity. Doubling the thickness of insulation doubles its R-value, assuming all other factors remain constant.
Recommended R-values vary by climate zone and building component. In the US, typical recommendations range from R-13 to R-21 for walls, R-30 to R-60 for attics, and R-25 to R-30 for floors, with higher values needed in colder climates.
For layers in series (such as a typical wall assembly), the total thermal resistance is the sum of the individual layer resistances: Rtotal = R1 + R2 + R3 + ... This principle allows engineers and architects to calculate the overall thermal performance of complex building assemblies.
The SI unit of thermal resistance. It represents the temperature difference in kelvins needed to transfer one watt of heat power through a material or system.
A unit commonly used in electronics thermal management. Since the kelvin and celsius scales have the same increment size, 1 K/W = 1 °C/W numerically.
The unit used for R-values in the United States building industry. It represents the temperature difference in fahrenheit needed to transfer one BTU of heat energy per hour through a material or system.
| Material/Assembly | Typical R-value (°F·h/BTU) | Equivalent (m²·K/W) |
|---|---|---|
| Single-pane glass | 1 | 0.18 |
| Double-pane glass | 2 | 0.35 |
| Triple-pane glass | 3-5 | 0.53-0.88 |
| Fiberglass batt (3.5") | 11-13 | 1.94-2.29 |
| Fiberglass batt (5.5") | 19 | 3.35 |
| Spray foam (closed cell, 1") | 6-7 | 1.06-1.23 |
| Rigid foam board (1") | 4-6.5 | 0.70-1.15 |
| Typical insulated wall (US) | 13-21 | 2.29-3.70 |
| Typical insulated ceiling (US) | 30-60 | 5.28-10.57 |
| Component/Interface | Typical Thermal Resistance (°C/W) | Application |
|---|---|---|
| CPU junction-to-case | 0.1-0.5 | Processor thermal design |
| Thermal interface material | 0.1-0.5 | Heat sink mounting |
| Small heat sink (passive) | 4-20 | Low-power components |
| Large heat sink with fan | 0.2-1.0 | High-performance CPUs |
| TO-220 transistor (junction-to-case) | 1.5-3.0 | Power electronics |
The temperature difference across a material or system can be calculated using thermal resistance:
Where:
This relationship is fundamental to thermal design in both building science and electronics cooling. It allows engineers to predict temperature differences based on heat flow and thermal resistance, or to determine the required thermal resistance to maintain a specific temperature difference.