Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Kilojoules (kJ)
8368.0000
Same number read as kilojoules → calories (kcal)
478.0115
1 kcal in kJ
4.184000
1 kJ in kcal
0.239006
10× your value in kJ
83680.000
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter value in calories (kcal) (kcal).
- 2Read your kilojoules (kj) on the right — it updates as you type.
- 3Hit Share to keep the scenario or send it to someone.
About this calculator
Food labels in Australia and the EU use kilojoules; the US uses kilocalories. Enter a value in calories (kcal) and this converter returns kilojoules along with the reverse direction, so you can sanity-check either way without re-typing.
Worked example
Using the values the calculator loads with:
Inputs
- Value in calories (kcal): 2000 kcal
Results
- Kilojoules (kJ): 8,368
- Same number read as kilojoules → calories (kcal): 478.0115
- 1 kcal in kJ: 4.184
- 1 kJ in kcal: 0.239006
- 10× your value in kJ: 83,680
What each field means
Inputs
- Value in calories (kcal) (kcal)
- The value in calories (kcal) used in the calculation, measured in kcal. Starts at 2000 kcal so you have a working example on load.
Results
- Kilojoules (kJ)
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Same number read as kilojoules → calories (kcal)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- 1 kcal in kJ
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- 1 kJ in kcal
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- 10× your value in kJ
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the calories (kcal) to kilojoules converter work?
Food labels in Australia and the EU use kilojoules; the US uses kilocalories. Enter a value in calories (kcal) and this converter returns kilojoules along with the reverse direction, so you can sanity-check either way without re-typing. The underlying maths is: Kilojoules = Calories (kcal) × 4.18400000
What do I need to enter?
Just one value: value in calories (kcal). Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the kilojoules (kj) result mean?
It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Estimates assume standard, average conditions — local rules, pricing, and materials vary.
Who is this tool for?
It's built for anyone doing everyday planning maths — a quick estimate that would otherwise need four browser tabs and a calculator app.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Calories (kcal) to Kilojoules Converter. Retrieved from https://www.revenuelab.fyi/toolbox/calories-to-kj
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/calories-to-kj" target="_blank" rel="noopener">Calories (kcal) to Kilojoules Converter — RevenueLab</a> (2026).</p>
Source: [Calories (kcal) to Kilojoules Converter — RevenueLab](https://www.revenuelab.fyi/toolbox/calories-to-kj) (2026).