kJ to kcal Converter

Common questions

How many kcal is 1,000 kJ?

239.005736138 kcal, because 1,000 / 4.184 = 239.005736138. The division scales straight up and down: 100 kJ is 23.9005736138 kcal, 250 kJ is 59.7514340344 kcal, 500 kJ is 119.502868069 kcal and 2,000 kJ is 478.011472275 kcal. Type any of them into the From box and the headline updates as you type, to twelve significant digits.

What is the formula for kJ to kcal?

kcal = kJ / 4.184, or kcal = kJ × 0.239005736138 if you would rather multiply. In the other direction kJ = kcal × 4.184, so 100 kcal is 418.4 kJ, 250 kcal is 1,046 kJ and 2,000 kcal is 8,368 kJ, all of them exact because the factor is exact and terminates. The Swap units button between the two boxes reverses the pair, so this page becomes a kcal to kJ converter without a reload.

Why does a food label print two energy numbers?

Because two units are in use for the same quantity. Labels in the EU and the UK declare energy in kilojoules and in kilocalories together, packs in Australia and New Zealand lead with kilojoules, and packs in the United States print Calories, which is the kilocalorie under another name. One food therefore carries a kJ figure and a kcal figure that are the same energy in different units, and 4.184 is the number between them.

Why do the kJ and kcal on my pack not divide out to exactly 4.184?

Two reasons, and neither is a mistake on the pack. The first is rounding: each figure is rounded on its own before printing, so 670 kJ beside 160 kcal is a pair of rounded numbers, not a division you can reverse (670 / 4.184 is 160.133843212). The second is that labelling energy is usually computed from per gram factors rather than converted, and the kJ and kcal factor sets are separately rounded: 17 kJ against 4 kcal a gram for carbohydrate and protein is a ratio of 4.25, and 37 kJ against 9 kcal for fat is 4.11. This converter does the arithmetic on the number you type and nothing else.

Is a kcal the same as a Calorie with a capital C?

Yes. One food Calorie is one kilocalorie, which is 1,000 small calories, so a 250 Calorie label figure is 250 kcal and 1,046 kJ. Watch the unit list on this page: the row named Calorie (cal) is the small calorie of 4.184 joules, and the row named Kilocalorie (kcal) is the food Calorie. For 1,000 kJ they read 239,005.736138 cal and 239.005736138 kcal, the same energy a thousand apart.

Which calorie does food energy use, 4.184 or 4.1868?

The thermochemical calorie of exactly 4.184 joules, and that is the one this page divides by. The 4.1868 figure is the international steam table calorie, a different definition kept for steam and engineering tables, and it is 0.0669 percent larger. On 2,000 kJ the two disagree by about three tenths of a kilocalorie: 478.011472275 kcal at 4.184 against 477.691793255 kcal at 4.1868. This converter holds 4.184 and has no switch for the other one.

Is dividing by 4.2 close enough?

It is 0.38 percent low, which is a fine head estimate and wrong in the last digits. 1,000 / 4.2 gives 238.095238095 against the exact 239.005736138. The other common shortcut, multiplying kilojoules by 0.24, lands 0.42 percent high and gives 240 for the same 1,000 kJ. Type the figure here if you want the digits to agree with the arithmetic rather than with a rule of thumb.

What else does this page show, and why does it open on kJ and kcal?

Under the answer it prints the same energy in joules, calories, watt hours, kilowatt hours and British thermal units at once, so 1,000 kJ also reads 277.777777778 Wh, 0.277777777778 kWh and 947.817120313 BTU; electronvolts sit behind the Show 1 more switch in the readout strip. It opens on kilojoules and kilocalories because a page that names a pair should show that pair, ahead of whatever the converter last remembered, and it leaves the main unit converter alone: go back to /unit-converter and it is still on the pair you left it on. The number you last typed does come with you. Copy result copies the headline exactly as printed, without the thousands separators.