Understanding BTU per Hour-Foot-Degree Fahrenheit to Milliwatts per Metre-Kelvin Conversion
BTU/(h·ft·°F) is the imperial thermal-conductivity unit on a per-foot thickness basis, used in process and piping engineering. mW/(m·K) is the SI unit scaled to milliwatts, well suited to reporting conductivities of insulating and low-conductivity materials. Converting between them aligns imperial industrial figures with metric material databases and building standards.
Conversion Formula
To convert BTU per Hour-Foot-Degree Fahrenheit to Milliwatts per Metre-Kelvin, multiply by this factor:
Step-by-Step Example
Convert 25 BTU per Hour-Foot-Degree Fahrenheit to Milliwatts per Metre-Kelvin.
How to Convert BTU per Hour-Foot-Degree Fahrenheit to Milliwatts per Metre-Kelvin
Translate a foot-basis imperial conductivity into metric milliwatts per metre-kelvin.
- Take the imperial value: Start with conductivity in BTU/(h·ft·°F).
- Multiply by 1730.735: This yields the equivalent in mW/(m·K).
- Optionally get W/(m·K): Divide the result by 1000 for watts per metre-kelvin.
- Report the result: mW/(m·K).
BTU per Hour-Foot-Degree Fahrenheit to Milliwatts per Metre-Kelvin conversion table
| BTU per Hour-Foot-Degree Fahrenheit (BTU/(h-ft-°F)) | Milliwatts per Metre-Kelvin (mW/(m-K)) |
|---|---|
| 0 | 0 |
| 1 | 1730.735 |
| 2 | 3461.469 |
| 3 | 5192.204 |
| 4 | 6922.939 |
| 5 | 8653.673 |
| 6 | 10384.41 |
| 7 | 12115.14 |
| 8 | 13845.88 |
| 9 | 15576.61 |
| 10 | 17307.35 |
| 15 | 25961.02 |
| 20 | 34614.69 |
| 25 | 43268.37 |
| 30 | 51922.04 |
| 40 | 69229.39 |
| 50 | 86536.73 |
| 60 | 103844.1 |
| 70 | 121151.4 |
| 80 | 138458.8 |
| 90 | 155766.1 |
| 100 | 173073.5 |
| 150 | 259610.2 |
| 200 | 346146.9 |
| 250 | 432683.7 |
| 300 | 519220.4 |
| 400 | 692293.9 |
| 500 | 865367.3 |
| 600 | 1038441 |
| 700 | 1211514 |
| 800 | 1384588 |
| 900 | 1557661 |
| 1000 | 1730735 |
| 2000 | 3461469 |
| 3000 | 5192204 |
| 4000 | 6922939 |
| 5000 | 8653673 |
| 10000 | 17307350 |
| 25000 | 43268370 |
| 50000 | 86536730 |
| 100000 | 173073500 |
| 250000 | 432683700 |
| 500000 | 865367300 |
| 1000000 | 1730735000 |
What is the BTU per Hour-Foot-Degree Fahrenheit?
The BTU per hour-foot-degree Fahrenheit is the customary unit of thermal conductivity in the United States and other imperial-using industries. It measures the heat, in British thermal units per hour, conducted through a material one foot thick for each degree Fahrenheit of temperature difference.
Definition
One BTU per hour-foot-degree Fahrenheit corresponds to a heat flow of one BTU per hour through a one-foot thickness for a one-degree-Fahrenheit temperature difference. In coherent SI units:
The exact value depends on the definition of the British thermal unit used; based on the International Table BTU (1055.05585262 J), 1 BTU/(h·ft·°F) = 1.730734666 W/(m·K).
Origin and History
The unit is built from three imperial and customary quantities: the British thermal unit (the heat needed to raise one pound of water by one degree Fahrenheit), the foot, and the Fahrenheit degree. It became the standard for U.S. thermal-property data long before SI was widely adopted and persists in North American engineering practice.
Law and Notable Facts
While the SI watt per metre-kelvin is preferred internationally, BTU/(h·ft·°F) remains entrenched in U.S. mechanical, HVAC and building codes. A useful benchmark: pure copper conducts at about 231 BTU/(h·ft·°F), roughly 400 times better than the fibreglass batts used to insulate walls.
Real-World Examples and Conversions
- Structural steel is about 26 BTU/(h·ft·°F); concrete roughly 0.8–1.0.
- Water conducts at about 0.35 BTU/(h·ft·°F).
- 1 BTU/(h·ft·°F) ≈ 1.7307 W/(m·K) ≈ 1730.7 mW/(m·K).
- Conversely, 1 W/(m·K) ≈ 0.5778 BTU/(h·ft·°F).
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).
Frequently Asked Questions
How many milliwatts per metre-kelvin is one BTU/(h·ft·°F)?
One BTU/(h·ft·°F) equals 1730.735 mW/(m·K).
How do I convert back to the imperial unit?
Multiply the mW/(m·K) value by 0.0005777893 to return to BTU/(h·ft·°F).
How does this relate to W/(m·K)?
Since 1730.735 mW/(m·K) is 1.730735 W/(m·K), just divide the milliwatt result by 1000 for the watt-per-metre-kelvin figure.
Why is the milliwatt unit convenient here?
It avoids small decimals when reporting the conductivity of insulating materials, giving readable whole-number magnitudes.
What is 25 BTU/(h·ft·°F) in mW/(m·K)?
25 BTU/(h·ft·°F) equals 43,268.38 mW/(m·K).
People also convert
Complete BTU per Hour-Foot-Degree Fahrenheit conversion table
| Unit | Result |
|---|---|
| Watts per Metre-Kelvin (W/(m-K)) | 1.730735 W/(m-K) |
| Milliwatts per Metre-Kelvin (mW/(m-K)) | 1730.735 mW/(m-K) |
| BTU-Inch per Hour-Square Foot-Degree Fahrenheit (BTU-in/(h-ft2-°F)) | 12 BTU-in/(h-ft2-°F) |
| Calories per Second-Centimetre-Degree Celsius (cal/(s-cm-°C)) | 0.004136555 cal/(s-cm-°C) |