Convert energy units — joules, calories, kilowatt-hours, BTU, kilojoules.
| Unit | Name | Value |
|---|---|---|
| J | Joule | 4184 |
| kJ | Kilojoule | 4.184 |
| cal | Calorie | 1000 |
| kWh | Kilowatt-hour | 0.0011622222 |
| BTU | BTU | 3.9656512 |
Formula: Kilojoule = Kilocalorie × 4.184
Multiply any kilocalorie value by 4.184 to get kilojoule.
Reverse: Kilocalorie = Kilojoule × 0.239
Common kilocalorie values — factor: 1 kcal = 4.184 kJ
| Kilocalorie (kcal) | Kilojoule (kJ) | Context |
|---|---|---|
| 1 kcal | 4.184 kJ | 1 kcal snack |
| 10 kcal | 41.84 kJ | Small fruit |
| 50 kcal | 209.2 kJ | Cookie |
| 100 kcal | 418.4 kJ | Small snack |
| 200 kcal | 836.8 kJ | Light meal |
| 500 kcal | 2,092 kJ | Workout burn |
| 1,000 kcal | 4,184 kJ | Large meal |
| 2,000 kcal | 8,368 kJ | Daily intake |
| 2,500 kcal | 1.046e+04 kJ | Active adult day |
| 5,000 kcal | 2.092e+04 kJ | Marathon burn |
| 1e+04 kcal | 4.184e+04 kJ | Ultra marathon |
| 5e+04 kcal | 2.092e+05 kJ | Week intake |
| 1e+05 kcal | 4.184e+05 kJ | Month intake |
| 1e+06 kcal | 4.184e+06 kJ | Year intake |
| 1.000e+09 kcal | 4.184e+09 kJ | Decade |
kcal × 4.184 = kJ. Round to × 4.2 for quick estimates (0.4% high).
A simple and memorable conversion anchor.
kJ ÷ 4.184 = kcal.
Prescribes daily energy intake and food portion sizes in kcal.
Calculates calorie burn during workouts and links to dietary targets.
Measures energy content of food products for nutritional labeling.
Creates weight management plans based on daily kcal targets.
Optimizes pre/during/post workout nutrition using kcal calculations.
Calculates nutritional information per serving in kcal for labels.
The kilocalorie (kcal) equals 1,000 calories or 4,184 joules, and is the unit used on food labels worldwide (often written as 'Cal' with a capital C in the US). It was standardized by the International Table calorie in 1956.
Nutritionists, dietitians, and food scientists use kcal for daily energy intake recommendations. Most adults need 2,000–2,500 kcal/day. Exercise apps, fitness trackers, and dietary plans all operate on kcal.
Interesting fact: One gram of fat yields about 9 kcal, one gram of carbohydrate or protein yields about 4 kcal. A single sugar cube (4g) contains about 16 kcal.
The kilojoule (kJ) equals 1,000 joules and is the practical energy unit for food, chemistry, and heating applications in metric countries. Food energy labels in Australia, Europe, and most of the world use kilojoules.
A dietary calorie (kcal) equals 4.184 kJ. A can of soda contains about 600 kJ. The specific heat of water (4.184 kJ/kg·°C) means heating 1 liter of water by 1°C requires 4.184 kJ.
Interesting fact: An average adult needs about 8,000-10,000 kJ (2,000-2,400 kcal) per day. Running a marathon burns approximately 12,500 kJ.
Converting kilocalorie to kilojoule is common across energy, nutrition, engineering, and science. Different sectors use different energy units — joules in physics, kcal in nutrition, kWh in electricity, and BTU in HVAC — making accurate conversion essential for cross-disciplinary work and international comparisons.
Quick reference: 5 kcal = 20.92 kJ and 10 kcal = 41.84 kJ. Reverse: 1 kJ = 0.239 kcal. Exact factor: 1 kcal = 4.184 kJ.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.