Calories to kJ Converter
Quick answer: To convert calories to kJ, multiply by 0.004184. For example, 10 cal is 0.04184 kJ. One calorie equals 0.004184 kJ.
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Use the Calories to kJ Converter
Calories to kJ formula and what each symbol means
kJ = cal × 0.004184
| Symbol | Meaning |
|---|---|
| cal | Calorie |
| kJ | Kilojoule |
Calories to kJ examples
1 cal
1 cal × 0.004184 = 0.004184 kJ.
10 cal
10 cal × 0.004184 = 0.04184 kJ.
100 cal
100 cal × 0.004184 = 0.4184 kJ.
Calories compared with kJ
One kJ is 239 times as large as one cal, so your number gets smaller when you convert calories to kJ and bigger when you convert back. If the answer is not smaller than what you typed, you multiplied instead of dividing.
About calories and kJ
Calorie (cal): The thermochemical calorie, exactly 4.184 joules. Kilojoule (kJ): 1,000 joules.
Where calories to kJ conversions are used
Food labels show kilocalories or kilojoules, and electricity bills use kilowatt-hours. Gas and heating are often billed in therms, BTU or megajoules.
How to calculate Calories to kJ step by step
- Enter the value in cal (the starting unit).
- Multiply by 0.004184, because 1 cal = 0.004184 kJ.
- The product is the value in kJ. To go back, divide by 0.004184 or multiply by 239.0057.
Popular energy conversions
How to read your Calories to kJ result
Quick estimate: multiply by about 0.0042 to get kJ from calories; this is within 0.4% of the exact factor. Food labels use the kilocalorie (kcal, written Calorie in the US), electricity bills use the kilowatt hour, and heating uses the Btu.
| CALORIES | KJ |
|---|---|
| 1 | 0.004184 |
| 2 | 0.008368 |
| 5 | 0.02092 |
| 10 | 0.04184 |
| 20 | 0.08368 |
| 50 | 0.2092 |
| 100 | 0.4184 |
| 1,000 | 4.184 |
kJ to Calories: quick table
| KJ | CALORIES |
|---|---|
| 1 | 239.0057 |
| 5 | 1,195.029 |
| 10 | 2,390.057 |
| 25 | 5,975.143 |
| 50 | 11,950.29 |
| 100 | 23,900.57 |
| 250 | 59,751.43 |
| 500 | 119,502.9 |
Common mistakes when calculating Calories to kJ
- Mixing the small calorie (cal) with the food Calorie (kcal): the difference is a factor of 1,000.
- Dividing when you should multiply: from cal to kJ multiply by 0.004184; from kJ to cal divide by 0.004184.
Calories to kJ FAQ
How many kJ are in 1 cal?
1 cal equals 0.004184 kJ.
How many cal are in 1 kJ?
1 kJ equals 239.0057 cal.
Is 1 cal = 0.004184 kJ an exact conversion?
Yes. The calorie and the kilojoule are both defined exactly in SI terms, so the ratio has no measurement uncertainty; 0.004184 is just that ratio shown to 7 significant figures.
What is a calorie (cal)?
The thermochemical calorie, exactly 4.184 joules.
How can I estimate calories to kJ in my head?
Quick estimate: multiply by about 0.0042 to get kJ from calories; this is within 0.4% of the exact factor.
What is 7 cal in kJ?
7 cal = 0.029288 kJ (since 7 × 0.004184).
What is 40 cal in kJ?
40 cal = 0.16736 kJ (since 40 × 0.004184).
What is 200 cal in kJ?
200 cal = 0.8368 kJ (since 200 × 0.004184).
How many decimals should I keep when converting cal to kJ?
Match the precision of your original measurement. For example, 0.04184 kJ rounds to 0.0418 kJ at 3 significant figures; keep more digits only for engineering or scientific work.
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Method, review and disclaimer
Edited by: Hemant Kumar and Anjita Rai, founders of ToolsVault (SEO and content professional, not a licensed adviser). Method: this tool runs in your browser using the formula shown on this page; the numbers you enter are not sent to our servers. Sources: NIST SP 811, Appendix B.8: conversion factors