Understanding Milliwatts per Metre-Kelvin to Watts per Metre-Kelvin Conversion
The milliwatt per metre-kelvin (mW/(m·K)) and the watt per metre-kelvin (W/(m·K)) are both SI-derived units of thermal conductivity, differing only by the metric prefix milli-. The watt per metre-kelvin is the primary SI unit used across engineering, materials science, and building physics, while milliwatts are handy for reporting the small conductivities of insulators and gases. This conversion is a simple decimal shift between the two prefixes.
Conversion Formula
To convert Milliwatts per Metre-Kelvin to Watts per Metre-Kelvin, multiply by this factor:
Step-by-Step Example
Convert 25 Milliwatts per Metre-Kelvin to Watts per Metre-Kelvin.
How to Convert Milliwatts per Metre-Kelvin to Watts per Metre-Kelvin
Shift between the two SI conductivity units by moving the decimal point.
- Recall the factor: One mW/(m·K) equals 0.001 W/(m·K).
- Take your value: Note the conductivity in milliwatts per metre-kelvin.
- Multiply: Multiply by 0.001 (or divide by 1000) to get watts per metre-kelvin.
- Result: For 25 mW/(m·K), the result is 25 × 0.001 = 0.025 W/(m·K).
Milliwatts per Metre-Kelvin to Watts per Metre-Kelvin conversion table
| Milliwatts per Metre-Kelvin (mW/(m-K)) | Watts per Metre-Kelvin (W/(m-K)) |
|---|---|
| 0 | 0 |
| 1 | 0.001 |
| 2 | 0.002 |
| 3 | 0.003 |
| 4 | 0.004 |
| 5 | 0.005 |
| 6 | 0.006 |
| 7 | 0.007 |
| 8 | 0.008 |
| 9 | 0.009 |
| 10 | 0.01 |
| 15 | 0.015 |
| 20 | 0.02 |
| 25 | 0.025 |
| 30 | 0.03 |
| 40 | 0.04 |
| 50 | 0.05 |
| 60 | 0.06 |
| 70 | 0.07 |
| 80 | 0.08 |
| 90 | 0.09 |
| 100 | 0.1 |
| 150 | 0.15 |
| 200 | 0.2 |
| 250 | 0.25 |
| 300 | 0.3 |
| 400 | 0.4 |
| 500 | 0.5 |
| 600 | 0.6 |
| 700 | 0.7 |
| 800 | 0.8 |
| 900 | 0.9 |
| 1000 | 1 |
| 2000 | 2 |
| 3000 | 3 |
| 4000 | 4 |
| 5000 | 5 |
| 10000 | 10 |
| 25000 | 25 |
| 50000 | 50 |
| 100000 | 100 |
| 250000 | 250 |
| 500000 | 500 |
| 1000000 | 1000 |
What is the Milliwatt per Metre-Kelvin?
The milliwatt per metre-kelvin is a unit of thermal conductivity equal to one thousandth of a watt per metre-kelvin. Its convenient scale makes it the preferred unit for describing thermal insulators and gases, whose conductivities are small fractions of a watt per metre-kelvin.
Definition
One milliwatt per metre-kelvin is 10⁻³ watt per metre-kelvin, the SI unit of thermal conductivity:
Like its parent unit, it may equivalently be written mW/(m·°C), since a one-kelvin interval equals a one-degree-Celsius interval.
Origin and History
The unit is simply the SI watt per metre-kelvin scaled by the standard milli- prefix (10⁻³). It became common in the insulation, cryogenics and gas-property literature during the twentieth century, where reporting figures such as 26 mW/(m·K) for air is clearer than 0.026 W/(m·K).
Law and Notable Facts
The milliwatt per metre-kelvin is a coherent SI unit with a decimal prefix and is legal for use worldwide. Building-insulation performance is often stated in mW/(m·K): the lower the value, the better the insulator, which is why manufacturers compete to push products below 30 mW/(m·K).
Real-World Examples and Conversions
- Dry air at room temperature conducts heat at about 26 mW/(m·K).
- Mineral wool and glass-fibre insulation typically fall between 30 and 40 mW/(m·K).
- Polyurethane foam boards reach roughly 22–25 mW/(m·K).
- 1 mW/(m·K) = 0.001 W/(m·K); conversely 1 W/(m·K) = 1000 mW/(m·K).
What is the Watt per Metre-Kelvin?
The watt per metre-kelvin is the SI coherent unit of thermal conductivity, quantifying how readily a material conducts heat. It expresses the rate of heat flow through a material per unit thickness for each degree of temperature difference across it.
Definition
A material has a thermal conductivity of one watt per metre-kelvin if a temperature gradient of one kelvin per metre drives a heat flux of one watt per square metre through it:
Because a temperature difference of one kelvin equals one degree Celsius, W/(m·K) and W/(m·°C) are numerically identical.
Origin and History
The unit follows directly from Fourier's law of heat conduction, published by Joseph Fourier in his 1822 Théorie analytique de la chaleur, which states that heat flux is proportional to the negative temperature gradient. The proportionality constant is the thermal conductivity, and it acquired its coherent SI form once the watt, metre and kelvin were established within the International System of Units.
Law and Notable Facts
The watt per metre-kelvin is the standard SI unit for material property tables worldwide. Thermal conductivity spans an enormous range: from aerogels near 0.02 W/(m·K), among the best solid insulators, to diamond at roughly 2000 W/(m·K), the highest of any bulk natural material.
Real-World Examples and Conversions
- Still air conducts heat at about 0.026 W/(m·K); water at about 0.6 W/(m·K).
- Common window glass is near 1.0 W/(m·K); stainless steel about 15 W/(m·K).
- Copper reaches roughly 400 W/(m·K), which is why it is used for heat sinks.
- 1 W/(m·K) = 1000 mW/(m·K) ≈ 0.5778 BTU/(h·ft·°F).
Frequently Asked Questions
How many watts per metre-kelvin equal one milliwatt per metre-kelvin?
One milliwatt per metre-kelvin equals exactly 0.001 watts per metre-kelvin, since milli- means one thousandth.
How do I convert mW/(m·K) to W/(m·K)?
Divide by 1000, or equivalently multiply by 0.001. For example, 25 mW/(m·K) equals 0.025 W/(m·K).
Why report conductivity in milliwatts per metre-kelvin?
Insulating materials and gases have very low conductivities, so milliwatts avoid awkward decimal fractions; for instance, air is roughly 26 mW/(m·K) rather than 0.026 W/(m·K).
How many milliwatts per metre-kelvin equal one watt per metre-kelvin?
Exactly 1000 milliwatts per metre-kelvin make up one watt per metre-kelvin.
Is this conversion exact?
Yes, because it is only a metric-prefix change, the factor of 0.001 is exact with no rounding involved.
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Complete Milliwatts per Metre-Kelvin conversion table
| Unit | Result |
|---|---|
| Watts per Metre-Kelvin (W/(m-K)) | 0.001 W/(m-K) |
| BTU per Hour-Foot-Degree Fahrenheit (BTU/(h-ft-°F)) | 0.0005777893 BTU/(h-ft-°F) |
| BTU-Inch per Hour-Square Foot-Degree Fahrenheit (BTU-in/(h-ft2-°F)) | 0.006933472 BTU-in/(h-ft2-°F) |
| Calories per Second-Centimetre-Degree Celsius (cal/(s-cm-°C)) | 0.000002390057 cal/(s-cm-°C) |