Molar Heat Capacity Converter

Reviewed by the CalculatorHub team, edited by James Graham. Exact thermal conversion factors. Last verified 17 June 2026.

Molar heat capacity is the heat needed to raise one mole of a substance by one kelvin, with the SI unit of joules per mole per kelvin (J/(mol.K)). For an ideal diatomic gas it is near 29 J/(mol.K). Chemists and engineers also use calories per mole per kelvin, kilojoules per kilomole per kelvin, and the customary BTU per pound-mole per degree Fahrenheit. This converter reduces a value to J/(mol.K) and converts out, using the exact factor 1 cal = 4.184 J (thermochemical calorie).

Value

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To unit

Converted value

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In joules per mole kelvin (J/mol.K)

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Molar heat capacity conversion

Base value (J/mol.K) = input * factor(from unit)
Output = base value / factor(to unit)
1 cal/(mol.K) = 4.184 J/(mol.K)
1 kJ/(kmol.K) = 1 J/(mol.K)
1 BTU/(lbmol.F) = 4.1868 J/(mol.K)

kJ/(kmol.K) is numerically identical to J/(mol.K). The cal factor uses the thermochemical calorie (4.184 J); the BTU factor uses the international table calorie (4.1868 J).

Molar heat capacity context

The SI unit is the joule per mole per kelvin (J/mol.K).
The universal gas constant R is about 8.314 J/(mol.K).
An ideal monatomic gas has a molar heat capacity at constant volume of 1.5 R, about 12.47 J/(mol.K).
kJ/(kmol.K) equals J/(mol.K) because both the energy and amount units scale by 1,000.
BTU per pound-mole per degree Fahrenheit is numerically equal to cal per mol per degree Celsius.

Molar heat capacity: frequently asked questions

Why does kJ/(kmol.K) equal J/(mol.K)?

A kilojoule is 1,000 joules and a kilomole is 1,000 moles, so the factor of 1,000 in the numerator and denominator cancels. The two units are numerically identical.

Which calorie is used?

The cal/(mol.K) factor uses the thermochemical calorie, defined as exactly 4.184 J. The BTU/(lbmol.F) factor uses the international table calorie, 4.1868 J, which is the convention for that customary unit.

What is the gas constant in these units?

The molar gas constant R is about 8.314 J/(mol.K), or equivalently about 1.987 cal/(mol.K). It is the difference between the molar heat capacities at constant pressure and constant volume for an ideal gas.

Why is BTU/(lbmol.F) close to cal/(mol.K)?

Because the ratio of the BTU to the calorie nearly matches the ratio of the pound-mole to the mole and the Fahrenheit to the Celsius degree, the combined factor lands at 4.1868 J/(mol.K), the international table calorie.

Is this specific heat?

No. Molar heat capacity is per mole; specific heat capacity is per unit mass (J/kg.K). They are related by the molar mass of the substance.

Official sources

NIST Special Publication 811: Guide for the Use of the International System of Units.
NIST: CODATA Recommended Values of the Fundamental Physical Constants.

Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.