kj to calories

KJ To Calories Formula & Conversion Factor (4.184)

The exact kJ to Calories formula, the 4.184 conversion factor and where it comes from, the reverse formula, mental shortcuts, and ready-to-paste Excel and Google Sheets formulas.

kJ to Calories Formula Calculator

kJ
Quick values
Common foods
1,000 kJ ÷ 4.184 = 239.01 kcal
Result
239.01 kcal
Food Calories (1 Calorie = 1 kcal)
56 minWalking
24 minRunning
29 minCycling
Share of an 8,700 kJ (2,079 kcal) day
11.5% of the average adult daily intake
Joules (J)1,000,000
Small calories (cal)239,006

Exercise times are estimates for a 70 kg adult.

On this page

The kJ To Calories Formula

Calories (kcal) = kilojoules (kJ) ÷ 4.184

Kilojoules (kJ) = Calories (kcal) × 4.184

The conversion factor is 4.184: one kilocalorie (a food Calorie) is exactly 4.184 kilojoules. Dividing by 4.184 is the same as multiplying by 0.239006, so you’ll also see the formula written as kcal = kJ × 0.239.

kJ to calories conversion formula infographic: kcal = kJ ÷ 4.184, with examples from 100 kJ to 8,700 kJ
The formula, the mental shortcut and common values.

Where Does 4.184 Come From?

The calorie was originally defined by heating water, but water’s heat capacity changes slightly with temperature, so the definition was never exact. Scientists fixed the problem by defining the thermochemical calorie directly in joules: 1 cal = 4.184 J exactly. Multiply both sides by 1,000 and you get 1 kcal = 4.184 kJ: the value used for food energy on labels and in nutrition science.

A second version, the International Steam Table calorie, is 4.1868 J. It’s used in some engineering contexts; the difference is under 0.07%, so it doesn’t matter for food.

Worked Examples

KilojoulesWorkingCalories
100 kJ100 ÷ 4.18423.90 kcal
575 kJ575 ÷ 4.184137.43 kcal
1,000 kJ1,000 ÷ 4.184239.01 kcal
2,100 kJ2,100 ÷ 4.184501.91 kcal
8,700 kJ8,700 ÷ 4.1842,079.35 kcal
More values in the kJ to calories chart.

And in reverse: 250 kcal × 4.184 = 1,046 kJ; 2,000 kcal × 4.184 = 8,368 kJ.

Mental-Maths Shortcuts

ShortcutkJ → kcalAccuracy
Divide by 41,000 → 2504.6% too high
Divide by 4, subtract 4%1,000 → 240within about 0.4%
Multiply by 0.241,000 → 240within about 0.4%
Divide by 4.21,000 → 2380.4% too low
For Calories → kJ, multiply by 4 and add 5%, or multiply by 4.2.

Excel And Google Sheets Formulas

If your kJ value is in cell A2:

  • kJ to Calories: =A2/4.184
  • Calories to kJ: =A2*4.184
  • Rounded to one decimal: =ROUND(A2/4.184,1)

These plain formulas work the same in Excel, Google Sheets, Numbers and LibreOffice.

Other Energy Units In The Same Family

FromToMultiply by
kJkcal (Calories)0.239006
kcalkJ4.184
kJcal (small calories)239.006
calJ4.184
kJJ1,000
MJkJ1,000
kJWh0.27778
For chemistry-style “cal” problems, see the kJ to cal chemistry converter.

Common Formula Mistakes

  • Multiplying when you should divide. kJ → kcal always gives a smaller number.
  • Using “cal” instead of “kcal”. 1,000 kJ is 239 kcal but 239,006 cal.
  • Double-converting a UK/EU label that already shows kcal.

FAQ

What is the formula for kJ to Calories?

Calories = kJ ÷ 4.184. For example, 500 kJ ÷ 4.184 = 119.5 Calories.

What is the conversion factor from kJ to Calories?

0.239006, or equivalently, divide by 4.184.

What is the formula for Calories to kJ?

kJ = Calories × 4.184. For example, 300 Calories × 4.184 = 1,255.2 kJ.

Why is the factor 4.184 and not 4.2?

4.184 is the exact defined value of the thermochemical calorie in joules. 4.2 is a rounded approximation.