Energy Unit Converter

Convert between Joule, Kilojoule, Calorie, Kilocalorie, kWh and BTU instantly. For diet, physics and engineering.

Instant result Runs in browser

Tip: "Calories" on food labels are actually kilocalories (kcal). "100 Calories" → 100 kcal = 418 kJ.

Food and activity energy values

kcalkJJ
1 g carbohydrate 4 16.7 16 736
1 g protein 4 16.7 16 736
1 g fat 9 37.7 37 656
1 g alcohol 7 29.3 29 288
Walking (30 min, 70 kg) ~140 ~585 ~585 000
Running (30 min, 70 kg) ~250 ~1 046 ~1 046 000
Average daily energy need 2 0008 368 8 368 000

Energy in Diet

Karbonhidrat 4 kcal / g
Protein 4 kcal / g
Yağ 9 kcal / g
Alkol 7 kcal / g
1 kcal = 4.184 kJ
1 kJ = 0.239 kcal
1 kWh = 860 kcal
1 BTU = 0.252 kcal

How to use?

  1. 1
    Enter a value Type your energy value in any unit field; all other units update instantly.
  2. 2
    Read the result Joule, kJ, kcal, kWh and BTU values appear simultaneously. No Calculate button needed.
  3. 3
    Apply to diet Enter the kJ value from a food label in the kJ field; kcal is calculated automatically.

FAQ

Are calories and kilocalories the same?
In everyday usage, "Calorie" (with a capital C) means kilocalorie (kcal). "200 Calories" on a food label means 200 kcal = 200,000 cal = 836,800 J. The small calorie (cal) is a scientific unit; 1 kcal = 1,000 cal.
How do I convert kJ to kcal?
1 kcal = 4.184 kJ. Divide the kJ value on a food label by 4.184 to get kcal. For example, 500 kJ ÷ 4.184 ≈ 120 kcal.
What is a BTU?
A BTU (British Thermal Unit) is the energy needed to raise 1 pound of water by 1°F. It is widely used in the US for air conditioning, heating, and cooling system capacities. 1 BTU ≈ 1,055 J ≈ 0.252 kcal.

Energy Units and Diet

Energy is the capacity to do work. The SI base unit is the Joule (J). In nutrition and fitness, kilocalories (kcal) are used; European food labels also show kilojoules (kJ).

Reading Food Labels

The "calorie" value on food labels is actually kilocalories (kcal). "100 Calories" → 100 kcal = 418 kJ = 418,000 J. Most labels show both kcal and kJ values.

Macronutrient Energy Values

  • Carbohydrates: 4 kcal/g = 16.7 kJ/g
  • Protein: 4 kcal/g = 16.7 kJ/g
  • Fat: 9 kcal/g = 37.7 kJ/g
  • Alcohol: 7 kcal/g = 29.3 kJ/g

Activity and Energy Expenditure

Estimated energy expenditure for a 70 kg person per hour: walking ~280 kcal, light jogging ~500 kcal, cycling ~400 kcal. These values vary significantly by individual and intensity.

kWh and Electrical Energy

1 kWh = 3,600,000 J = 860 kcal — roughly equivalent to 3 hours of moderate exercise. Understanding this connection between energy units bridges physics and nutritional science.

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