Use this kJ/kg·K to BTU/lb·°F Converter to convert specific heat capacity values between metric and imperial units. Enter a value in kilojoules per kilogram per Kelvin, and the tool converts it into British thermal units per pound per degree Fahrenheit. You can also use the reverse converter to change BTU/lb·°F to kJ/kg·K.
This converter is useful for thermodynamics, heat transfer, HVAC calculations, material property tables, engineering reports, and academic work. Specific heat values are often listed in different unit systems, so a clean conversion helps you compare water, air, metals, fuels, oils, refrigerants, and other materials without doing manual unit math.
What Is kJ/kg·K?
kJ/kg·K means kilojoules per kilogram per Kelvin. It is a metric unit used for specific heat capacity, which tells you how much heat energy is needed to raise the temperature of one kilogram of a material by one Kelvin.
For example, water has a specific heat capacity close to 4.1868 kJ/kg·K. That means it takes about 4.1868 kilojoules of heat to raise 1 kilogram of water by 1 Kelvin. Metals usually have lower values, while water is high because it stores a large amount of heat for its mass.
What Is BTU/lb·°F?
BTU/lb·°F means British thermal units per pound per degree Fahrenheit. It is the imperial unit commonly used for specific heat capacity, especially in HVAC, heat exchanger work, U.S. engineering references, and equipment manuals.
A value in BTU/lb·°F shows how many BTUs are required to raise the temperature of one pound of a substance by one degree Fahrenheit. Water is often shown as about 1 BTU/lb·°F, which is why water is a common reference material in heat transfer calculations.
How to Use the kJ/kg·K to BTU/lb·°F Converter
Enter your specific heat value in the left box to convert kJ/kg·K to BTU/lb·°F. The calculator multiplies your value by the conversion factor and displays the result instantly. This is useful when your source data is in SI units but your project, assignment, or equipment documentation uses imperial units.
Use the right box when you need to convert BTU/lb·°F to kJ/kg·K. Enter the BTU/lb·°F value, click convert, and the tool returns the equivalent metric specific heat value. This reverse conversion is helpful when reading U.S. HVAC data, heat transfer charts, or older engineering references.
kJ/kg·K to BTU/lb·°F Formula
To convert kJ/kg·K to BTU/lb·°F, multiply the kJ/kg·K value by the conversion factor. Your tool uses the displayed factor of 0.239006 for this conversion.
For example, if the specific heat value is 45 kJ/kg·K, the conversion is:
BTU/lb·°F to kJ/kg·K Formula
To convert BTU/lb·°F to kJ/kg·K, multiply the BTU/lb·°F value by 4.1868. This gives the metric specific heat capacity value in kilojoules per kilogram per Kelvin.
For example, if the value is 23 BTU/lb·°F, the reverse conversion is:
Specific Heat Capacity Formula
Specific heat capacity is connected to heat energy, mass, and temperature change. In physics and engineering, the common heat equation is q = m × c × ΔT, where q is heat energy, m is mass, c is specific heat capacity, and ΔT is the temperature change.
When you rearrange the equation to solve for specific heat capacity, the formula becomes:
This is why the unit includes energy, mass, and temperature together. In metric form, that can be written as kJ/kg·K. In imperial form, it can be written as BTU/lb·°F.
kJ/kg·K, kJ/kg·°C, and Temperature Difference
For specific heat capacity, kJ/kg·K and kJ/kg·°C often have the same numeric value because a temperature change of 1 Kelvin is equal in size to a temperature change of 1 degree Celsius. The units are different in notation, but the temperature interval size is the same.
That means a specific heat value written as 4.1868 kJ/kg·K may also appear as 4.1868 kJ/kg·°C in many practical engineering tables. The same idea applies to BTU/lb·°F and BTU/lb·°R when the unit is used for temperature difference, not absolute temperature.
J/kg·K to BTU/lb·°F
If your value is in J/kg·K instead of kJ/kg·K, convert joules to kilojoules first. Since 1 kJ equals 1000 J, divide the J/kg·K value by 1000 before using the kJ/kg·K to BTU/lb·°F conversion.
For example, 4186.8 J/kg·K is equal to 4.1868 kJ/kg·K. After that, you can convert the kJ/kg·K value into BTU/lb·°F using the main converter.
Quick Conversion Table
The table below gives common kJ/kg·K to BTU/lb·°F values. These are useful for checking results quickly when working with specific heat capacity data.
| kJ/kg·K | BTU/lb·°F |
|---|---|
| 0.1 | 0.023901 |
| 0.5 | 0.119503 |
| 1 | 0.239006 |
| 2 | 0.478012 |
| 3 | 0.717018 |
| 4 | 0.956024 |
| 4.1868 | About 1.0007 |
| 5 | 1.19503 |
The reverse table below helps when your value starts in BTU/lb·°F and you need kJ/kg·K.
| BTU/lb·°F | kJ/kg·K |
|---|---|
| 0.1 | 0.41868 |
| 0.5 | 2.0934 |
| 1 | 4.1868 |
| 2 | 8.3736 |
| 3 | 12.5604 |
| 5 | 20.934 |
Where This Converter Is Used
This specific heat converter is useful in thermodynamics problems where material properties are listed in one unit system and your calculation uses another. Students often use it when solving heat transfer, energy balance, boiler, turbine, cooling, and thermal storage problems.
Engineers may use the converter when comparing international equipment data. A material property table may list specific heat in kJ/kg·K, while an HVAC document may use BTU/lb·°F. Converting the unit helps keep the calculation consistent and reduces mistakes caused by mixing metric and imperial values.
Common Materials and Specific Heat Values
Different materials absorb heat differently. Water has a high specific heat capacity, which is why it is commonly used in heating and cooling systems. Metals such as aluminum, copper, and steel generally have lower specific heat values, so they heat up and cool down faster than water.
| Material | Approx. Specific Heat | Common Unit |
|---|---|---|
| Water | 4.1868 | kJ/kg·K |
| Aluminum | 0.897 | kJ/kg·K |
| Copper | 0.385 | kJ/kg·K |
| Steel | About 0.46 to 0.50 | kJ/kg·K |
| Air | About 1.005 | kJ/kg·K |
These values are general references. For design work, use the exact value from your textbook, data sheet, engineering standard, or material property table because specific heat can change with temperature, pressure, and material composition.
kJ/kg·K vs kJ/kg to BTU/lb
This page is made for kJ/kg·K to BTU/lb·°F, which is a specific heat capacity conversion. It is not the same as a plain kJ/kg to BTU/lb conversion, which is specific energy or enthalpy per unit mass without temperature in the unit.
The difference matters because the conversion factor is not the same when the temperature part is removed. Use this tool only when your unit includes a temperature interval such as K, °C, °F, or °R. If your unit is only kJ/kg, you need a specific energy converter instead.
Common Mistakes to Avoid
Do not remove the temperature part of the unit when converting specific heat. A value written as kJ/kg·K has a different meaning from kJ/kg. The “per Kelvin” part tells you the value relates to temperature change, not only energy per mass.
Also avoid confusing lb with lbf. In BTU/lb·°F, lb means pound mass. It does not mean pound force. Many people type BTU/lbf by mistake, but the correct unit for this converter is BTU per pound per degree Fahrenheit.
FAQs
What does kJ/kg·K mean?
kJ/kg·K means kilojoules per kilogram per Kelvin. It measures specific heat capacity, or the amount of heat energy needed to raise one kilogram of a material by one Kelvin.
What does BTU/lb·°F mean?
BTU/lb·°F means British thermal units per pound per degree Fahrenheit. It is the imperial unit for specific heat capacity and is common in HVAC and U.S. engineering references.
How do you convert kJ/kg·K to BTU/lb·°F?
Multiply the kJ/kg·K value by 0.239006. For example, 45 kJ/kg·K multiplied by 0.239006 equals 10.7553 BTU/lb·°F.
How do you convert BTU/lb·°F to kJ/kg·K?
Multiply the BTU/lb·°F value by 4.1868. For example, 23 BTU/lb·°F multiplied by 4.1868 equals 96.2964 kJ/kg·K.
Is kJ/kg·K the same as kJ/kg·°C?
For temperature difference in specific heat calculations, kJ/kg·K and kJ/kg·°C have the same numeric value because a change of 1 Kelvin equals a change of 1 degree Celsius.
Is BTU/lb·°F the same as BTU/lb·°R?
For temperature difference, BTU/lb·°F and BTU/lb·°R are often numerically equivalent because a degree Fahrenheit interval and a Rankine interval have the same size.
Can I convert J/kg·K to BTU/lb·°F?
Yes. Divide the J/kg·K value by 1000 to convert it into kJ/kg·K, then multiply by 0.239006 to get BTU/lb·°F.
Is kJ/kg to BTU/lb the same conversion?
No. kJ/kg to BTU/lb is a specific energy conversion. kJ/kg·K to BTU/lb·°F is a specific heat capacity conversion, so the temperature part of the unit must be included.
Why do some sources show slightly different conversion factors?
Small differences can happen because BTU definitions and rounding choices vary between references. For normal engineering and homework use, the displayed rounded conversion factors are usually enough.
Where is this converter useful?
It is useful in thermodynamics, heat transfer, HVAC, material science, energy balance calculations, heat exchanger work, and engineering coursework where specific heat units must be converted between metric and imperial systems.
