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Kilojoules to kilocalories converter

Convert kilojoules to kilocalories (kJ to kcal) with the exact factor, a conversion chart and worked steps.

Updated Checked against 3 worked examples

kJ
Try
Kilocalories
kcal
Kilocalories: 2,079.3499044 kcal
Shown to 12 significant figures, half-up
Conversion
8,700 kJ = 2,079.3499043977 kcal
1 kcal in kilojoules
4.184kJ

8,700 kilojoules is 2,079.3499043977 kilocalories. Going the other way, 1 kcal is 4.184 kJ.

Kilojoules to kilocalories

05001,0001,5002,0002,0004,0006,0008,00010,000kJkcal8,700 → 2,079.3499
KJ to kcal chart (9 rows)
KilojoulesKilocalories
10023.9006
25059.7514
500119.5029
1000239.0057
2000478.0115
41841,000
50001,195.0287
87002,079.3499
100002,390.0574
How it's calculated S
  1. Conversion factor

    1 kJ=0.239005736138 kcal1\ \text{kJ} = 0.239005736138\ \text{kcal}

    Rounded here for display; the calculation uses 50 significant digits.

  2. Multiply

    8,700×0.239005736138=2,079.3499044 kcal8{,}700 \times 0.239005736138 = 2{,}079.3499044\ \text{kcal}

About the kilojoules to kilocalories converter

Kilojoules on a food label may need conversion to the kilocalorie scale used in a diary. The arithmetic changes the energy unit, not the portion size. A daily total requires summing the energy for the portions actually recorded.

One kilojoule is about 0.2390057361 kilocalories, so 8700 kJ is 2,079.349904 kcal. To convert kJ to kcal, multiply by 0.2390057361; to convert back, multiply by 4.184.

The kilocalorie used on food labels is the thermochemical kilocalorie, exactly 4.184 kJ. The factor has no exact decimal form, so results are computed with 50 significant digits and rounded only for display.

Worked examples

8700 kJ to kcal

Kilojoules (kJ)
8700 kJ
Kilocalories
2,079.3499044 kcal

Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

1000 kJ to kcal

Kilojoules (kJ)
1000 kJ
Kilocalories
239.005736138 kcal

Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

100 kJ to kcal

Kilojoules (kJ)
100 kJ
Kilocalories
23.9005736138 kcal

Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

Questions

When would I convert kJ to kcal?

Kilojoules on a food label may need conversion to the kilocalorie scale used in a diary. The arithmetic changes the energy unit, not the portion size. A daily total requires summing the energy for the portions actually recorded.

How many kilocalories are in a kilojoule?

One kilojoule is about 0.2390057361 kilocalories. The kilocalorie used on food labels is the thermochemical kilocalorie, exactly 4.184 kJ.

How do you convert kJ to kcal?

Multiply the number of kilojoules by 0.2390057361. For example, 8700 kJ × 0.2390057361 = 2,079.349904 kcal. To go the other way, divide by 0.2390057361.

How can I estimate kJ to kcal without a calculator?

Multiply by 0.24. That is 0.4% high of the exact factor 0.2390057361, so 8700 kJ comes out as 2,088 kcal instead of 2,079.3499.

How accurate is the kilojoules to kilocalories converter?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 3 worked examples whose answers come from independent sources; for example, “8700 kJ to kcal” is checked against Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions).

Where does the method come from?

NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B; NIST Handbook 44, Appendix C: General tables of units of measurement; BIPM, The International System of Units (SI Brochure), 9th edition.

About this calculator

kilocalories=kilojoules×0.239005736138\text{kilocalories} = \text{kilojoules} \times 0.239005736138

Sources

  1. NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B
  2. NIST Handbook 44, Appendix C: General tables of units of measurement
  3. BIPM, The International System of Units (SI Brochure), 9th edition

Checked against references

3 worked examples with independently sourced answers ship with this calculator. They run in the test suite; you can run them here too.

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