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Calories to Joules Converter (Thermochemical)
↔ Convert J to cal instead

Common Conversions

cal J
0.1 0.4184
0.5 2.092
1 4.184
5 20.92
10 41.84
25 104.6
50 209.2
100 418.4
250 1046
500 2092
1000 4184
5000 20920

Why this conversion matters in chemistry

Thermochemistry of the early twentieth century used several different calorie definitions — the thermochemical calorie (4.184 J), the IT calorie (4.1868 J), the 15 °C calorie (4.1855 J) — each defined operationally against a slightly different way of warming water. Modern chemistry settled on the thermochemical calorie as the standard, with the conversion factor pinned at exactly 4.184 J. The conversion is what lets a pre-SI literature value land cleanly on a modern data table without losing the 0.05% spread between calorie definitions, which is usually below the experimental uncertainty anyway but worth keeping track of for high-precision work.

Formula

J = cal × 4.184

Worked Examples

1 cal = 4.184 J

One thermochemical calorie — the conversion anchor, defined exactly as 4.184 J.

1000 cal = 4184 J

One kilocalorie — the same as one nutritional Calorie, the unit on every food label.

18 cal = 75.3 J

Approximately the molar heat capacity of liquid water at 25 °C, around 75.3 J/(mol·K) or 18 cal/(mol·K).

13700 cal = 57321 J

About the standard enthalpy of neutralization for a strong acid with a strong base — roughly −13.7 kcal/mol, equivalent to −57 kJ/mol.

Frequently Asked Questions

How do I convert calories to joules?
Multiply by 4.184 for the thermochemical calorie. So 250 cal becomes 1046 J. The factor is exact, so the conversion introduces no rounding error of its own.
Are there really different kinds of calories?
Yes — the thermochemical calorie at exactly 4.184 J is the chemistry standard, but the 15 °C calorie (4.1855 J) and the IT calorie (4.1868 J) also appear in older literature. The 0.05% spread between them rarely matters but is worth checking if a value is being propagated to high precision.
Where does the calorie come from?
Originally, the calorie was defined as the heat needed to raise 1 gram of water by 1 °C. Water's specific heat varies slightly with temperature, which is why several operational definitions emerged. The thermochemical calorie collapsed all that into a fixed value of 4.184 J, removing the temperature dependence.
How does this fit into a calorimetry calculation?
If specific heat is tabulated in cal/(g·°C), the q = mcΔT result comes out in cal and gets multiplied by 4.184 to become joules. Alternatively, use c in J/(g·°C) directly — water is 4.184 J/(g·°C), which is the same constant doing double duty as the conversion factor.