Joules to Calories Converter
Convert energy between joules, calories, and kilocalories using the standard conversion factors.
Converter
Results
Joules (J)
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Kilojoules (kJ)
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Calories (cal)
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Kilocalories (kcal)
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Steps
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Joule vs calorie: the definition
A joule (J) is the SI unit of energy. A calorie (cal) in this context is the thermochemical small calorie, defined as:
1 cal = 4.184 J
1 kcal = 1000 cal = 4184 J
Food labels usually use kcal but write “Calories” with a capital C.
Formulas
J → cal: \( \text{cal} = \dfrac{\text{J}}{4.184} \)
J → kcal: \( \text{kcal} = \dfrac{\text{J}}{4184} \)
cal → J: \( \text{J} = \text{cal} \times 4.184 \)
kcal → J: \( \text{J} = \text{kcal} \times 4184 \)
kJ → J: \( \text{J} = \text{kJ} \times 1000 \)
FAQ
Does it use 4.184 or 4.2?
This tool uses the more precise 4.184 J per cal (thermochemical). Some textbooks round to 4.2 J, which is OK for quick physics problems but less exact.
Can I convert kJ directly to kcal?
Yes: first convert kJ → J (×1000) then J → kcal (÷4184). The calculator performs both steps at once.
Formula (LaTeX) + variables + units
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1 cal = 4.184 J 1 kcal = 1000 cal = 4184 J
J → cal: \( \text{cal} = \dfrac{\text{J}}{4.184} \) J → kcal: \( \text{kcal} = \dfrac{\text{J}}{4184} \) cal → J: \( \text{J} = \text{cal} \times 4.184 \) kcal → J: \( \text{J} = \text{kcal} \times 4184 \) kJ → J: \( \text{J} = \text{kJ} \times 1000 \)
- No variables provided in audit spec.
- CDC — Health topics — cdc.gov · Accessed 2026-01-19
https://www.cdc.gov/ - NIH — Health information — nih.gov · Accessed 2026-01-19
https://www.nih.gov/health-information - WHO — Health topics — who.int · Accessed 2026-01-19
https://www.who.int/health-topics
Last code update: 2026-01-19
- Initial audit spec draft generated from HTML extraction (review required).
- Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
- Confirm sources are authoritative and relevant to the calculator methodology.