Understanding Calories per Second-Centimetre-Degree Celsius to BTU-Inch per Hour-Square Foot-Degree Fahrenheit Conversion
The calorie per second-centimetre-degree Celsius, cal/(s-cm-°C), is a CGS unit of thermal conductivity long used in physics and materials-science literature, especially older tables of metal and mineral properties. The BTU-inch per hour-square foot-degree Fahrenheit, BTU-in/(h-ft2-°F), is the imperial unit favoured by the US insulation industry, where conductivity is reported per inch of thickness. Converting between them bridges classical scientific data and North American product specifications.
Conversion Formula
To convert Calories per Second-Centimetre-Degree Celsius to BTU-Inch per Hour-Square Foot-Degree Fahrenheit, multiply by this factor:
Step-by-Step Example
Convert 25 Calories per Second-Centimetre-Degree Celsius to BTU-Inch per Hour-Square Foot-Degree Fahrenheit.
How to Convert Calories per Second-Centimetre-Degree Celsius to BTU-Inch per Hour-Square Foot-Degree Fahrenheit
Use this procedure to translate a CGS conductivity into the imperial per-inch unit.
- Record the CGS value: Start with the conductivity in cal/(s-cm-°C), such as 25.
- Multiply by the factor: Use 2900.965, the number of BTU-in/(h-ft2-°F) in one cal/(s-cm-°C).
- Work out the product: .
- Report the answer: 25 cal/(s-cm-°C) equals 72524.1 BTU-in/(h-ft2-°F).
Calories per Second-Centimetre-Degree Celsius to BTU-Inch per Hour-Square Foot-Degree Fahrenheit conversion table
| Calories per Second-Centimetre-Degree Celsius (cal/(s-cm-°C)) | BTU-Inch per Hour-Square Foot-Degree Fahrenheit (BTU-in/(h-ft2-°F)) |
|---|---|
| 0 | 0 |
| 1 | 2900.965 |
| 2 | 5801.929 |
| 3 | 8702.894 |
| 4 | 11603.86 |
| 5 | 14504.82 |
| 6 | 17405.79 |
| 7 | 20306.75 |
| 8 | 23207.72 |
| 9 | 26108.68 |
| 10 | 29009.65 |
| 15 | 43514.47 |
| 20 | 58019.29 |
| 25 | 72524.11 |
| 30 | 87028.94 |
| 40 | 116038.6 |
| 50 | 145048.2 |
| 60 | 174057.9 |
| 70 | 203067.5 |
| 80 | 232077.2 |
| 90 | 261086.8 |
| 100 | 290096.5 |
| 150 | 435144.7 |
| 200 | 580192.9 |
| 250 | 725241.1 |
| 300 | 870289.4 |
| 400 | 1160386 |
| 500 | 1450482 |
| 600 | 1740579 |
| 700 | 2030675 |
| 800 | 2320772 |
| 900 | 2610868 |
| 1000 | 2900965 |
| 2000 | 5801929 |
| 3000 | 8702894 |
| 4000 | 11603860 |
| 5000 | 14504820 |
| 10000 | 29009650 |
| 25000 | 72524110 |
| 50000 | 145048200 |
| 100000 | 290096500 |
| 250000 | 725241100 |
| 500000 | 1450482000 |
| 1000000 | 2900965000 |
What is the Calorie per Second-Centimetre-Degree Celsius?
The calorie per second-centimetre-degree Celsius is the CGS-based unit of thermal conductivity, historically common in physics and physical-chemistry literature. It measures the heat in calories flowing per second through a one-centimetre thickness for each degree Celsius of temperature difference.
Definition
One calorie per second-centimetre-degree Celsius represents a heat flow of one calorie per second through a one-centimetre cube per degree Celsius across it. Using the thermochemical calorie (4.184 J):
The value follows from 4.184 J/s per (0.01 m · 1 K) = 4.184 ÷ 0.01 = 418.4 W/(m·K). If the International Table calorie (4.1868 J) is used instead, the factor is 418.68 W/(m·K).
Origin and History
The unit arose in the CGS era, when heat was measured in calories, lengths in centimetres and temperature in degrees Celsius. It appears throughout older thermal-conductivity tables and heat-transfer texts, especially in chemistry and metallurgy, before the watt per metre-kelvin became standard.
Law and Notable Facts
Though largely superseded by SI, the unit is still encountered in legacy data and some scientific traditions. Its large size is convenient for metals: because 1 cal/(s·cm·°C) equals 418.4 W/(m·K), even highly conductive copper is under 1 in these units, whereas most materials are small fractions.
Real-World Examples and Conversions
- Copper conducts at about 0.94 cal/(s·cm·°C), i.e. roughly 400 W/(m·K).
- Iron is about 0.18 cal/(s·cm·°C).
- Water is roughly 0.0014 cal/(s·cm·°C).
- 1 cal/(s·cm·°C) = 418.4 W/(m·K); conversely 1 W/(m·K) ≈ 0.00239 cal/(s·cm·°C).
What is the BTU-Inch per Hour-Square Foot-Degree Fahrenheit?
The BTU-inch per hour-square foot-degree Fahrenheit is the unit of thermal conductivity most commonly used for building and insulation materials in the United States. It states the heat, in BTU per hour, conducted through one square foot of a material one inch thick per degree Fahrenheit of temperature difference.
Definition
The unit uses inch thickness and square-foot area rather than foot thickness, making it exactly one twelfth of the BTU per hour-foot-degree Fahrenheit:
Based on the International Table BTU, the exact value is 0.144227889 W/(m·K), i.e. 1.730734666 ÷ 12.
Origin and History
Insulation and building products are thin sheets or boards, so engineers found it natural to express conductivity per inch of thickness across a square foot of area. This "k-value" convention became the North American standard for insulation datasheets and is the basis of the R-value system, where R = thickness (inches) ÷ k-value.
Law and Notable Facts
The unit underpins U.S. insulation labelling. The R-value printed on insulation is derived from this conductivity: a lower k-value in BTU·in/(h·ft²·°F) yields a higher R-value per inch, meaning better insulation. Typical fibreglass batt has a k-value near 0.25–0.30.
Real-World Examples and Conversions
- Rigid polyisocyanurate foam has a k-value of about 0.14 BTU·in/(h·ft²·°F), giving roughly R-7 per inch.
- Softwood lumber is about 0.8 BTU·in/(h·ft²·°F).
- 1 BTU·in/(h·ft²·°F) ≈ 0.14423 W/(m·K) ≈ 144.23 mW/(m·K).
- Because it is 1/12 of BTU/(h·ft·°F), 12 BTU·in/(h·ft²·°F) = 1 BTU/(h·ft·°F).
Frequently Asked Questions
How many BTU-in/(h-ft2-°F) are in one cal/(s-cm-°C)?
Exactly 2900.965 BTU-in/(h-ft2-°F) per cal/(s-cm-°C). The CGS unit is very large, so the imperial equivalent is a big number.
How do I reverse the conversion?
Multiply the BTU-in/(h-ft2-°F) value by 0.0003447129 to return to cal/(s-cm-°C). For instance, 2900.965 BTU-in/(h-ft2-°F) maps back to 1 cal/(s-cm-°C).
Why is the imperial unit expressed "per inch"?
US insulation datasheets normalize conductivity to a one-inch thickness, giving BTU-in/(h-ft2-°F). This makes it easy to multiply by material thickness in inches to estimate heat flow through a panel.
What kind of material has a conductivity near 1 cal/(s-cm-°C)?
Highly conductive metals such as copper approach roughly 1 cal/(s-cm-°C), which is why the imperial figure is so large; insulation materials are thousands of times smaller.
Is this the same as thermal conductance?
No. Conductivity is an intrinsic material property; conductance (and U-value) depend on the specific thickness and area of a component. Convert conductivity first, then account for geometry.
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Complete Calories per Second-Centimetre-Degree Celsius conversion table
| Unit | Result |
|---|---|
| Watts per Metre-Kelvin (W/(m-K)) | 418.4 W/(m-K) |
| Milliwatts per Metre-Kelvin (mW/(m-K)) | 418400 mW/(m-K) |
| BTU per Hour-Foot-Degree Fahrenheit (BTU/(h-ft-°F)) | 241.7471 BTU/(h-ft-°F) |
| BTU-Inch per Hour-Square Foot-Degree Fahrenheit (BTU-in/(h-ft2-°F)) | 2900.965 BTU-in/(h-ft2-°F) |