What this converter does
This converter turns specific heat capacity between BTU/lb·°F, kJ/kg·K, J/kg·K and cal/g·°C — instantly and with exact factors. Type a value, pick the units, and read the answer as you type. Handy for reading US thermal tables into SI units.
BTU/lb·°F and cal/g·°C are numerically equal, so water is ~1 in both and ~4.186 kJ/kg·K. For the temperature scales themselves, see the Fahrenheit to Celsius converter.
The units it covers
Every unit is specific heat capacity, so each converts through the J/kg·K with a fixed ratio.
View all units & their values
| Unit | Symbol | Value | Mainly used |
|---|---|---|---|
| BTU per lb·°F | BTU/lb·°F | 4186.8 | US thermal engineering |
| Kilojoule per kg·K | kJ/kg·K | 1000 | SI-based, engineering tables |
| Joule per kg·K | J/kg·K | 1 | SI base unit |
| Calorie per g·°C | cal/g·°C | 4184 | Chemistry (water ≈ 1) |
The formula
Each unit has a fixed value in J/kg·K, so any conversion goes through it once:
result = value × factor_from ÷ factor_toWhere:
- value = the number you typed, in the “from” unit
- factor_from = the “from” unit’s value in J/kg·K
- factor_to = the “to” unit’s value in J/kg·K
Worked example
Convert water’s 1 BTU/lb·°F to kJ/kg·K.
BTU/lb·°F = 4186.8 · kJ/kg·K = 10001 × 4186.8 ÷ 1000 = 4.187 kJ/kg·KSo 1 BTU/lb·°F is about 4.187 kJ/kg·K — the specific heat of water.
The units in this example
The US thermal-engineering unit. Numerically identical to cal/g·°C, so water is about 1 in both — the reference the BTU was defined from.
- water ≈ 1 BTU/lb·°F
- 1 BTU/lb·°F = 4186.8 J/kg·K
- 1 BTU/lb·°F = 1 cal/g·°C
- 1 BTU/lb·°F ≈ 4.187 kJ/kg·K
The SI-based engineering unit of specific heat — energy to raise one kilogram by one kelvin. Water is about 4.186 kJ/kg·K.
- water ≈ 4.186 kJ/kg·K
- 1 kJ/kg·K ≈ 0.2388 BTU/lb·°F
- 1 kJ/kg·K = 1,000 J/kg·K
- air ≈ 1.005 kJ/kg·K