Thermal Conductivity Converter
Convert thermal conductivity between W/m·K, kW/m·K, W/cm·K, cal/s·cm·K, and BTU-based units. Enter a value, then choose the From unit and To unit.
Convert Thermal Conductivity Between Units
Thermal Conductivity Formula
Where:
- \(k_{\mathrm{from}}\) — thermal conductivity value entered
- \(k_{\mathrm{to}}\) — converted thermal conductivity value
- \(F_{\mathrm{from}}\) — factor that converts one From unit to W/m·K
- \(F_{\mathrm{to}}\) — factor that converts one To unit to W/m·K
The calculator first converts the entered value to W/m·K, then divides by the factor for the selected output unit. It displays the result rounded to eight decimal places.
Thermal Conductivity – Calculation Example
Example: Convert the default value of 0.5 W/m·K to BTU/h·ft·°F.
\[ k_{\mathrm{to}}=0.5\frac{1}{1.730735}\approx 0.28889460\ \mathrm{BTU/(h\cdot ft\cdot {}^\circ F)} \]
Result: approximately 0.2888946 BTU/h·ft·°F.
How to use the calculator
- Enter a nonnegative number in Thermal conductivity value. For example, leave the default 0.5 to follow the calculation above.
- Choose the unit attached to that number in From unit. The default is W/m·K.
- Choose the unit you need in To unit. The default is BTU/h·ft·°F.
- Read Converted Thermal Conductivity, which includes the selected output unit. To check a different conversion, change either unit and use the new result.
If From unit and To unit are the same, the numerical value does not change. A unit conversion changes how a conductivity is expressed, not the material property itself.
What thermal conductivity means
Thermal conductivity describes how readily heat moves through a material when there is a temperature difference. Its symbol is commonly \(k\). A higher conductivity generally means heat can pass through the material more easily; a lower conductivity is often desirable for insulation. Conductivity is a material property, not a measure of how much heat an entire wall, pipe, or component transfers on its own.
For a simple, steady, one-dimensional layer of thickness \(L\), the magnitude of conductive heat flux can be expressed as \(q''=k\Delta T/L\). This relationship shows why conductivity matters: for the same thickness and temperature difference, increasing \(k\) increases heat flow per unit area. Actual heat transfer can also depend on geometry, contact between materials, and other heat-transfer mechanisms.
Conductivity values appear in building insulation specifications, electronics cooling calculations, and process equipment data. Sources may use SI units or BTU-based units, so converting them to a common unit helps you compare values. If you need to calculate heat flow rather than convert \(k\), use the Heat Transfer calculator. For a heat-flow rate per unit area, see the Heat Flux Density converter.
Supported units and conversion factors
Each factor below is the number of W/m·K represented by one unit of the listed conductivity. These are the factors used by this calculator:
- W/m·K: 1
- kW/m·K: 1,000
- W/cm·K: 100
- cal/s·cm·K: 418.68
- BTU/h·ft·°F: 1.730735
- BTU/s·ft·°F: 6,238.6464
For example, a value in kW/m·K is multiplied by 1,000 to obtain W/m·K. A value in W/m·K is divided by 100 to obtain W/cm·K. The calorie and BTU entries use the calculator’s preset factors; they are not additional material properties.
Assumptions and practical limits
This converter changes conductivity units only. It does not account for how conductivity may vary with temperature, material composition, moisture, or direction within a material. When comparing published values, check that they refer to comparable conditions. Also distinguish thermal conductivity from specific heat: specific heat concerns energy needed to change temperature, not the rate at which heat conducts through a material.
The K and °F in these conductivity units refer to temperature differences, not absolute temperatures. For a temperature difference, a change of 1 K equals a change of 1 °C; Fahrenheit-sized differences require a scale conversion. Do not add a temperature offset when converting thermal conductivity.
Check BTU/s results for critical use: the calculator’s two BTU factors are not consistent with the 3,600 seconds in an hour. Multiplying its BTU/h·ft·°F factor, 1.730735, by 3,600 gives 6,230.646 W/m·K, rather than its preset 6,238.6464 for BTU/s·ft·°F. Conversions involving BTU/s·ft·°F may therefore disagree with a conversion based solely on changing hours to seconds. Verify the required factor independently before using such a result in engineering work.
Frequently Asked Questions
How can I convert thermal conductivity by hand?
Convert the starting value to W/m·K, then convert that result to your target unit. For example, 2 W/cm·K equals 200 W/m·K because a meter contains 100 centimeters. Since 1 kW/m·K equals 1,000 W/m·K, the same value is 0.2 kW/m·K. Write the units alongside each step to catch multiplication or division mistakes.
What is a typical thermal conductivity value?
There is no single normal value; it depends strongly on the material. Many insulation products are around 0.02–0.05 W/m·K, water is about 0.6 W/m·K near room temperature, and common metals can range from tens to hundreds of W/m·K. These are rough reference values, not specifications: temperature, composition, and measurement conditions matter.
Why does W/cm·K convert to a larger number in W/m·K?
The number becomes 100 times larger because the length unit appears in the denominator: 1 meter is 100 centimeters. Thus, 1 W/cm·K equals 100 W/m·K. A common mistake is dividing by 100 because centimeters are smaller. Keeping the full unit in view makes the direction of the conversion easier to check.
How is thermal conductivity different from R-value or U-value?
Thermal conductivity describes a material, while an R-value describes resistance to heat flow through a particular thickness. For a uniform layer, resistance per unit area is \(R''=L/k\), where \(L\) is thickness. A U-value describes overall heat transfer through an assembly and also accounts for its other layers and relevant surface resistances.
Why do sources give different conductivities for the same material?
They may be reporting values measured under different conditions. Conductivity can change with temperature, moisture, density, composition, and, for some materials, the direction of heat flow. Before comparing two figures, check their test conditions and whether each describes a solid material, an insulation product, or an entire assembly.
Can thermal conductivity be zero or negative?
A negative conductivity is not a valid value for an ordinary passive material. Zero can be entered in the converter, but real materials generally have some capacity to conduct heat; a reported zero may instead be a placeholder or a value rounded too aggressively. Check the source before treating it as a physical property.
How many digits of a converted result should I use?
Use no more meaningful digits than the original measurement supports. The converter displays eight decimal places, but that display precision does not make the source value more accurate. Very small converted values may also appear as zero after rounding. For engineering work, retain an unrounded intermediate value and check any unit factors required by your reference.
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