Specific Heat Capacity Converter: J/(kg·K), Btu/(lb·°F) & More
Convert specific heat (cp, cv)—energy per mass per temperature change—between SI, calorie, and Btu units.
Convert specific heat capacity between J/(kg·K), Btu/(lb·°F), cal/(g·°C), kcal/(kg·K), and 20 units. For thermodynamics, HVAC, and material science. Free, runs in your browser—no sign-up.
What is specific heat capacity?
Specific heat capacity c is the energy required to raise one unit mass by one degree of temperature. It depends on mass and temperature change and is central to heating and cooling calculations:
where Q is heat added, m is mass, and ΔT is the temperature change. SI unit is J/(kg·K). Note: Btu/(lb·°C) uses a different scale than Btu/(lb·°F)—one °C is 1.8× one °F, so the numerical factor differs. This converter includes both so you can match US and metric sources.
Engineers use it for enthalpy change (Q = m·c·ΔT), HVAC load, and material selection. Water has c ≈ 4186 J/(kg·K); metals are often 400–500; gases lower. All 20 units are converted via J/(kg·K) under the hood.
Key units explained
J/(kg·K)
Factor: 1 (SI base)
Standard unit. Same as J/(kg·°C) because 1 Δ°C = 1 K. Water ≈ 4186 J/(kg·K).
Btu/(lb·°F)
Factor: 1 ≈ 4186.8 J/(kg·K)
Common in US HVAC and process engineering. Same numerical ballpark as cal/(g·°C).
cal/(g·°C)
Factor: 1 ≈ 4186.8 J/(kg·K)
Chemistry and food science. 1 cal (IT)/(g·°C) ≈ 4187 J/(kg·K). Cal (th) uses 4184.
Btu/(lb·°C)
Factor: 1 ≈ 2326 J/(kg·K)
Per degree Celsius (larger than °F), so fewer J per kg per °C. Less common than Btu/(lb·°F).
Who uses this converter?
HVAC and process engineers convert between Btu/(lb·°F) and J/(kg·K) for load calculations and equipment specs. Chemists and food scientists work in cal/(g·°C) or kcal/(kg·K). Students need to unify units for Q = m·c·ΔT. With 20 units including mechanical (kgf·m/(kg·K), lbf·ft/(lb·°R)) and CHU, this converter covers textbooks and datasheets. All conversions run locally.
Common conversions at a glance
| From | To | Formula |
|---|---|---|
| Btu/(lb·°F) | J/(kg·K) | × 4186.8 |
| cal/(g·°C) | J/(kg·K) | × 4186.8 |
| kJ/(kg·K) | J/(kg·K) | × 1000 |
Avoiding common mistakes
Don’t confuse Btu/(lb·°F) with Btu/(lb·°C)—they differ by a factor of 1.8 because one °C is 1.8× one °F. Calorie (IT) and (th) differ slightly (4186.8 vs 4184 J per gram per °C); we support both. For Q = m·c·ΔT, make sure ΔT is in the same temperature scale as c (e.g. if c is in J/(kg·K), use ΔT in K or °C). When in doubt, convert c to J/(kg·K) and ΔT to kelvin.
Specific Heat Capacity FAQ
? How do I convert Btu/(lb·°F) to J/(kg·K)?
Multiply by about 4186.8. So 1 Btu (IT)/(lb·°F) ≈ 4186.8 J/(kg·K). The factor comes from 1 Btu ≈ 1055 J, 1 lb ≈ 0.454 kg, and 1 °F = 5/9 K. Use the converter above for cal/(g·°C), Btu/(lb·°C), and other variants.
? Why is Btu/(lb·°C) different from Btu/(lb·°F)?
Because one degree Celsius is 1.8 times one degree Fahrenheit. So the same physical specific heat expressed “per °C” has a smaller number than “per °F”: 1 Btu/(lb·°F) ≈ 2326 Btu/(lb·°C) in equivalent J/(kg·K) terms. This converter includes both so you can match either convention.
? What is the specific heat of water?
Liquid water is about 4186 J/(kg·K) or 1 cal/(g·°C) (by definition of the calorie). So 1 Btu/(lb·°F) ≈ 1 in those units for water. Use the converter to express that in kcal/(kg·K), CHU/(lb·°C), or any of the 20 supported units.
? How do I convert cal/(g·°C) to J/(kg·K)?
Multiply by 4186 (thermochemical) or about 4187 (IT). So 1 cal/(g·°C) ≈ 4186 J/(kg·K)—same numerical value as water’s specific heat. Use the converter for cal/(g·K), Btu/(lb·°C), and 18 other units.
? What is specific heat capacity and how is it used in Q = mcΔT?
Specific heat c is the energy needed to raise one unit mass by one degree. In Q = mcΔT, Q is heat, m is mass, c is specific heat, ΔT is temperature change. Use consistent units: if c is in J/(kg·K), m in kg and ΔT in K give Q in joules. This converter keeps c in the unit you need.
? What is the specific heat of air or common materials?
Air at constant pressure is about 1005 J/(kg·K). Steel ~500, aluminum ~900, copper ~385 J/(kg·K). Use this converter when your table is in Btu/(lb·°F) or cal/(g·°C) and your calculation uses J/(kg·K), or for CHU/(lb·°C) and other variants.