kJ to Calories Converter
Two units share the name calorie, and this page opens on the smaller one. The calorie (cal) in the To box is the thermochemical calorie of exactly 4.184 joules, so kilojoules to calories is cal = kJ × 1,000 / 4.184, which makes 1 kJ 239.005736138 cal, 10 kJ 2,390.05736138 cal and 1,000 kJ 239,005.736138 cal. The Calorie with a capital C on a food label is the other one: it is the kilocalorie, a thousand small calories, and it has its own row in the list under the answer, where the same 1,000 kJ reads 239.005736138 kcal. If the number you are converting came off a pack, the kcal row is the one that matches the label. Both directions are short: 1,000 cal is exactly 4.184 kJ, and 4.184 kJ typed into the From box returns exactly 1,000 cal. This page opens with Kilojoule (kJ) in the From box and Calorie (cal) in the To box, ahead of whatever pair the converter last remembered, prints twelve significant digits, and lists the same energy in joules, kilocalories, watt hours, kilowatt hours and British thermal units at once. It converts units and nothing else: it knows nothing about what the energy is in and gives no dietary guidance.
1 kJ in every energy unit
Common questions
- How many calories is 1 kJ?
- 239.005736138 small calories, because 1,000 / 4.184 = 239.005736138. In food Calories, which are kilocalories, the same kilojoule is 0.239005736138 kcal. The division scales straight up: 10 kJ is 2,390.05736138 cal, 100 kJ is 23,900.5736138 cal, 600 kJ is 143,403.441683 cal and 2,000 kJ is 478,011.472275 cal.
- Is the calorie on this page the same as the Calorie on a food label?
- No, and the difference is a factor of 1,000. A label Calorie, written with a capital C, is a kilocalorie: the row named Kilocalorie (kcal) in the list under the answer. The row named Calorie (cal) is the small calorie of 4.184 joules that the headline shows. For 1,000 kJ the two read 239,005.736138 cal and 239.005736138 kcal, the same energy a thousand apart. To put the label figure in the headline, pick Kilocalorie (kcal) in the To menu.
- What is the formula for kJ to calories?
- cal = kJ × 1,000 / 4.184, or cal = kJ × 239.005736138 if you would rather multiply once. For the food Calorie it is kcal = kJ / 4.184. The reverse direction is exact and terminates, because the factor is exact: kJ = cal × 0.004184, so 1,000 cal is 4.184 kJ, 100 cal is 0.4184 kJ and 250 kcal is exactly 1,046 kJ. The swap button between the two boxes reverses the pair without a reload.
- Which calorie is this, 4.184 joules or 4.1868?
- The thermochemical calorie of exactly 4.184 joules, which is also the factor used for food energy labelling, and this converter has no switch for the other one. The 4.1868 figure is the international steam table calorie, kept for steam and engineering tables, and it is 0.0669 percent larger. Under that definition a kilojoule would read about 238.845897 cal instead of the 239.005736138 cal this page prints, a gap that first shows up in the third significant digit. There is also a 15 degree calorie of about 4.1855 joules, defined from heating water by one degree, which is why the name needs a qualifier at all.
- Worked example: a 600 kJ snack and an 8,700 kJ day
- 600 kJ is 143,403.441683 cal, which the kcal row reads as 143.403441683 kcal. The 8,700 kJ used as the reference intake on Australian and New Zealand labels is 2,079,349.9044 cal, or 2,079.3499044 kcal. Other common label figures land the same way: 500 kJ is 119.502868069 kcal, 1,500 kJ is 358.508604207 kcal and 2,000 kJ is 478.011472275 kcal. These are unit conversions of a number you type, nothing more.
- How do I convert calories back to kilojoules?
- Press the swap button between the boxes and the page becomes calories to kilojoules: 1 cal gives 0.004184 kJ, 100 cal gives 0.4184 kJ and 1,000 cal gives exactly 4.184 kJ. For food Calories, choose Kilocalorie (kcal) in the From menu after swapping, where 1 kcal is 4.184 kJ and 250 kcal is 1,046 kJ. Every figure in that direction terminates, because 4.184 is exact.
- What else does the page show for 1 kJ?
- The same energy in every common energy unit at once: 1,000 J, 239.005736138 cal, 0.239005736138 kcal, 0.277777777778 Wh, 0.000277777777778 kWh and 0.947817120313 BTU. The readout strip carries a Show 1 more switch for the uncommon unit, the electronvolt, where 1 kJ reads 6.241509e21 eV. Anything below 0.000001 or at 1e15 and above is printed in exponential notation rather than as a row of zeroes.
- Why does the page open on kilojoules and calories when I last converted something else?
- Because a page that names a pair should show that pair. This one sets kilojoules and calories on arrival, ahead of whatever the converter last remembered, and it leaves the main unit converter alone: go back to the converter itself and it is still on the pair you left it on. The number you last typed does travel with you. Copy result copies the headline exactly as printed but without the thousands separators, and each row of the list has its own Copy button.
Conversion factors are the exact legal definitions where one exists. An inch is exactly 2.54 cm and a pound exactly 0.45359237 kg, so those conversions are exact rather than approximate. Temperature uses offsets rather than factors, and that is shown in the working.