Heat converters
Thermal Conductivity Converter
Convert W/(m·K), BTU/(h·ft·°F), kcal/(h·m·°C) and other conductivity units.
Result
0.577789 BTU/(h·ft·°F)
1 W/(m·K) = 0.577789 BTU/(h·ft·°F)
All units for this value
| Unit | Symbol | Value |
|---|---|---|
| Watt per meter per kelvin | W/(m·K) | 1 |
| Milliwatt per meter per kelvin | mW/(m·K) | 1000 |
| Kilowatt per meter per kelvin | kW/(m·K) | 0.001 |
| Watt per centimeter per degree Celsius | W/(cm·°C) | 0.01 |
| Kilocalorie (IT) per hour per meter per °C | kcal/(h·m·°C) | 0.859845 |
| Calorie (IT) per second per cm per °C | cal/(s·cm·°C) | 0.00238846 |
| BTU (IT) per hour per foot per °F | BTU/(h·ft·°F) | 0.577789 |
| BTU (IT) inch per hour per ft² per °F | BTU·in/(h·ft²·°F) | 6.93347 |
| BTU (IT) per second per foot per °F | BTU/(s·ft·°F) | 0.000160497 |
About this calculator
Thermal conductivity measures how readily a material conducts heat through its bulk, a core property used in insulation ratings, materials selection, and heat transfer calculations. This converter switches between watts per meter-kelvin, BTU per hour-foot-°F, and kilocalorie per hour-meter-°C, covering the metric, US customary, and calorie-based systems commonly seen in engineering references.
How it works in plain English
Thermal conductivity describes the rate of heat flow through a unit thickness of material per unit area, for each degree of temperature difference across it. The converter uses watts per meter-kelvin as its common anchor, since that's the standard SI form, and rescales into other units by combining the appropriate length, time, energy, and degree-size factors for each unit.
US customary units like BTU per hour-foot-°F combine several imperial building blocks at once: the BTU as the energy unit, the hour as the time unit, the foot as the length unit, and the Fahrenheit degree as the temperature unit. Converting from the SI form requires adjusting for all four factors simultaneously, which is why the numeric conversion factor, about 1.730735, isn't an obviously round number. Kilocalorie-based units follow a similar pattern using the calorie as the energy unit and the Celsius degree, which shares the same size as a kelvin.
Choose your starting and target units in the from and to menus, enter a conductivity value, and the result appears immediately alongside a table showing the same value across every supported unit. A precision control adjusts the number of decimal places shown, and a swap button reverses the two selected units in a single click.
The formula
- value_in_target = value_in_source × (source factor to W/(m·K)) ÷ (target factor to W/(m·K))
- 1 BTU/(h·ft·°F) ≈ 1.730735 W/(m·K)
- 1 kcal/(h·m·°C) ≈ 1.163 W/(m·K)
- 1 W/(cm·°C) = 100 W/(m·K)
Worked example
Suppose a material datasheet lists a thermal conductivity of 0.04 BTU/(h·ft·°F), typical of a rigid foam insulation panel, and an engineer working from metric drawings wants that value in the SI form used in most engineering calculations. Multiplying by the conversion factor gives 0.04 × 1.730735 = 0.0692 W/(m·K).
Entering 0.04 into the BTU/(h·ft·°F) field with W/(m·K) selected as the target returns about 0.0692 W/(m·K) immediately. As a sanity check, that figure sits close to the roughly 0.03-0.04 W/(m·K) range typically quoted for rigid foam insulation, confirming the conversion landed in a physically sensible place rather than off by a factor of ten. The full unit table also shows this equals roughly 0.0596 kcal/(h·m·°C), confirming the value against a third common reference system without needing a separate calculation by hand.
Typical thermal conductivity of common materials
| Material | Approx. conductivity (W/(m·K)) |
|---|---|
| Copper | 400 |
| Aluminium | 237 |
| Steel (carbon) | 50 |
| Glass | 1.0 |
| Water (liquid) | 0.6 |
| Rigid foam insulation | 0.03-0.04 |
| Air (still) | 0.026 |
Commonly cited engineering material property values
Frequently asked questions
Why do metals have such high thermal conductivity compared to insulation materials?
Metals conduct heat efficiently because free electrons within their structure can rapidly carry thermal energy through the material, in addition to vibrating atoms passing energy along. Insulating materials like foam lack that mobile electron structure and often trap pockets of still air, which conducts heat very poorly, so both effects combine to make insulation far less conductive than metal.
Why does converting to BTU-based units involve a factor around 1.73 instead of something rounder?
The BTU-based unit combines four separate imperial quantities at once: energy in BTU, time in hours, length in feet, and temperature in Fahrenheit degrees. Each of those has its own conversion relationship to the metric equivalents, and multiplying all four factors together produces 1.730735, a number that isn't round simply because the historical unit systems weren't designed to align neatly.
Is thermal conductivity the same as an insulation R-value?
No. Thermal conductivity is a property of the material itself, independent of thickness, while R-value describes the resistance of a specific layer of material at a specific thickness. A material with low conductivity still needs enough thickness to achieve a meaningful R-value, so the two figures serve different but related purposes.
Why is air's conductivity so low compared to water?
Gas molecules in air are spread far apart and transfer heat mainly through relatively infrequent collisions, making conduction slow. Water molecules are packed much more closely together, allowing energy to pass between neighboring molecules more readily, which gives liquid water a conductivity roughly twenty times higher than still air.
Can I use this converter for heat flow calculations directly?
This tool only converts the conductivity value itself between unit systems; it doesn't calculate total heat flow, which also depends on a material's thickness, cross-sectional area, and the temperature difference across it. Once you have a consistent conductivity figure in the right units, you can plug it into a separate heat transfer formula or calculator.
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