Specific Heat Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/10/2026
To convert a specific heat, it is reduced to a common unit (the joule per kilogram-kelvin), then converted into the new unit. The specific heat of water, 4184 J/(kg·K), equals exactly 1 cal/(g·°C) — a coincidence that isn't one, since the calorie was historically defined from this property of water.
Explanation
Specific heat (or specific heat capacity) measures the amount of energy needed to raise the temperature of one kilogram of a substance by one degree. The joule per kilogram-kelvin (J/(kg·K)) is the SI unit, but two other units remain widely used depending on context: the calorie per gram-degree Celsius (cal/(g·°C)), historically defined from water itself (a calorie originally being the energy needed to raise one gram of water by one degree Celsius), and the BTU per pound-degree Fahrenheit (BTU/(lb·°F)), used in the United States in industry and thermal engineering. The apparent coincidence between 4184 J/(kg·K) and exactly 1 cal/(g·°C) is not one: the modern calorie (the thermochemical calorie, fixed at exactly 4.184 joules) was defined precisely to make these two values match, water having served as the historical reference for the unit itself. The BTU/(lb·°F), by contrast, does not coincide exactly with these values (4186.8 J/(kg·K), a gap of about 0.07% due to the distinct definitions of the BTU, the pound, and the degree Fahrenheit — the same BTU as in our energy conversion calculator) — a small but real difference, not to be silently rounded to 4184 in a precise technical calculation. To calculate an amount of heat from a known specific heat (Q = mass × specific heat × temperature change), see our specific heat calculator, which takes this value as an input rather than converting it.
Example: specific heat of water, 4184 J/(kg·K) to cal/(g·°C)
Inputs
Value: 4184. Starting unit: J/(kg·K). Target unit: cal/(g·°C).
Calculation
4184 ÷ 4184 (factor of the calorie per gram-degree Celsius) = 1.
Result
The specific heat of water is exactly 1 cal/(g·°C).
Frequently asked questions
Why does 4184 J/(kg·K) correspond exactly to 1 cal/(g·°C)?
Because the modern thermochemical calorie is defined by convention as exactly 4.184 joules, a definition chosen precisely so that this relationship with water — the historical reference substance of the calorie — remains exactly, not approximately, true.
Why does the BTU/(lb·°F) not coincide exactly with the other two units?
Because the BTU, the pound, and the degree Fahrenheit each have their own independent historical definition, with no direct link to the definition of the calorie or the kilogram. The result, once converted, is close to 4184 J/(kg·K) (4186.8 precisely) but not rigorously equal to it — a gap of about 0.07%, small but measurable in a precise technical calculation.
Is this conversion enough to calculate an amount of heat exchanged?
No, this calculator only converts the value of the specific heat itself between unit systems. To calculate the amount of heat actually exchanged during a temperature change (Q = mass × specific heat × temperature change), use our dedicated specific heat calculator, which takes the specific heat as an input.