Kilocalories to Kilojoules Calculator
Enter kilocalories to find kilojoules. kJ = kcal × 4.184.
How the result changes
Only kilocalories changes; all other inputs stay at your current values. The line illustrates the formula across the shown range. This is not a forecast of real-world outcomes.
About this calculation
Convert kilocalories (kcal) to kilojoules (kJ) while preserving the underlying energy quantity. The calculator updates when the input changes and shows the conversion rule and a worked example.
Formula
kJ = kcal × 4.184
Worked example
With Kilocalories: 1 kcal, kilojoules is 4.184 kJ.
How to convert kilocalories to kilojoules
Enter a value in kilocalories. Multiply it by the factor in the displayed formula to express the same quantity in kilojoules. To reverse the relationship, divide by the same nonzero factor.
kJ = kcal × 4.184. As a reference point, 10 kcal equals 41.84 kJ with this conversion. This is an example, not a recommended level or target.
What the unit relationship means
Kilocalories and kilojoules express quantities of energy. Energy can describe electrical consumption, transferred heat, or mechanical work; the unit conversion changes the number but not the kind of event that supplied it. Keep a unit of power, such as a watt, separate from an energy unit, such as a watt-hour. Power needs a duration before it becomes an energy amount, so a kcal-to-kJ conversion alone cannot tell you how long a device ran.
Check the direction of the result
As a scale check, one kcal corresponds to 4.184 kJ. Doubling the input from 10 kcal to 20 kcal changes the calculated output from 41.84 kJ to 83.68 kJ. Ordinary factor conversions are proportional: zero maps to zero and doubling the input doubles the result. If a copied value does not follow this pattern, check the source unit, decimal point, and formula direction.
When this conversion is useful
Compare food energy or heat quantities stated in kilocalories and kilojoules. The symbol cal means a small calorie, while kcal means a kilocalorie.
What to check
One kilocalorie is 1,000 small calories. A nutrition label’s capital-C Calorie generally means one kilocalorie, so read the unit and capitalization carefully. In this direction the entered kilocalories is reported as kilojoules; check both unit symbols when copying a figure from another source, because the reverse direction answers a different question.
Precision and reporting
Energy labels, meters, and specifications may round their values differently. Retain the unit and enough digits to avoid compounding rounding error in later calculations, but do not present a rough source estimate as an exact measurement. If comparing bills or food labels, also check the reporting period or serving size. For a separate reporting example, 7.3 kcal produces 30.5432 kJ. If 7.3 kcal was an approximate reading, the converted digits should not be treated as a more accurate measurement.
Common questions
What is the reverse of kilocalories to kilojoules?
To return from kJ to kcal, divide by the nonzero factor shown in this calculator's formula.
Inputs
- Kilocalories (kcal)