Specific Heat Converter
Convert between J/(kg·K), kJ/(kg·K), cal/(g·°C), and BTU/(lb·°F) instantly.
Type in any field and the others update automatically.
Type in any field — the others update instantly.
Specific heat is the energy it takes to raise one kilogram of a substance by one kelvin (or one degree Celsius, since the size of the step is identical). The SI unit is the joule per kilogram-kelvin, J/(kg·K). It’s the reason some things heat up in seconds and others seem to take forever.
Key conversions:
- 1 kJ/(kg·K) = 1,000 J/(kg·K)
- 1 cal/(g·°C) = 4,186.8 J/(kg·K)
- 1 BTU/(lb·°F) = 4,186.8 J/(kg·K)
It’s no accident that the calorie and BTU versions land on the same number. Both were originally defined around water, so they convert to SI identically.
Where common materials sit:
- Water: 4,187 J/(kg·K)
- Aluminum: about 900 J/(kg·K)
- Iron: about 450 J/(kg·K)
- Copper: about 385 J/(kg·K)
Water’s value is unusually high, and that one fact shapes the planet. Oceans absorb and release enormous amounts of heat with only small temperature swings, which is why coastal climates stay milder than inland ones, and why a pot of water takes its time coming to a boil.
Keep one distinction clear: specific heat is per kilogram. Heat capacity without the “specific” is the total for a whole object. A swimming pool and a cup of water share the same specific heat but hold wildly different total heat capacities.
How we build and check this converter
This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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