Last updated: September 16, 2026
Quick answer: Multiply food calories (kcal) by 4.184 to get kilojoules (kJ). 1 kcal = 4.184 kJ. So 100 kcal = 418.4 kJ, 500 kcal = 2,092 kJ, and a typical 2,000 kcal daily intake = 8,368 kJ. To go the other way, see our kJ to calories converter.
Kilocalorie to Kilojoule
Instantly convert kilocalorie to kilojoule with fast, accurate, real-time results.
Formula: calories to kilojoules
One food calorie (kilocalorie, kcal) equals exactly 4.184 kilojoules. This is the thermochemical calorie — the amount of energy needed to raise 1 kilogram of water by 1°C.
Examples:
- 95 kcal (medium apple) × 4.184 = 397.5 kJ
- 250 kcal (small meal) × 4.184 = 1,046 kJ
- 600 kcal (restaurant main) × 4.184 = 2,510 kJ
- 2,000 kcal (daily intake) × 4.184 = 8,368 kJ
Calories vs kcal — what's on food labels?
The term "calorie" is famously confusing because it's used in two ways:
- Food calorie (Cal, kcal): The "Calories" on nutrition labels in the US and UK are actually kilocalories (kcal). So "200 Calories" on a cereal box means 200 kcal = 836.8 kJ.
- Small calorie (cal): The scientific calorie — 1/1,000 of a food calorie. Rarely used outside physics and chemistry labs. 1 cal = 0.004184 kJ.
In Australia, New Zealand, most of Europe, and medical literature, food energy is expressed in kilojoules (kJ). A can of cola labeled "630 kJ" in Sydney is the same as "150 kcal" (Calories) in New York.
| Label says | Country / region | What it means | Equivalent |
|---|---|---|---|
| Calories or Cal (capital C) | US, Canada | kcal (food calories) | 1 Cal = 4.184 kJ |
| kcal | UK, EU, international | kilocalories | 1 kcal = 4.184 kJ |
| kJ | Australia, NZ, EU | kilojoules | 1 kJ = 0.239 kcal |
| cal (lowercase) | Science / lab use | small calories | 1,000 cal = 1 kcal |
Common foods in kcal and kJ
These values are approximate averages — actual energy content varies by brand, preparation method, and portion size. Values shown are per standard serving.
| Food / drink | Serving | kcal | kJ |
|---|---|---|---|
| Apple (medium) | 182 g | 95 kcal | 397 kJ |
| Banana (medium) | 118 g | 105 kcal | 439 kJ |
| Orange (medium) | 131 g | 62 kcal | 259 kJ |
| Boiled egg (large) | 50 g | 77 kcal | 322 kJ |
| White bread slice | 28 g | 75 kcal | 314 kJ |
| Cooked white rice (1 cup) | 186 g | 242 kcal | 1,013 kJ |
| Chicken breast (grilled) | 140 g | 231 kcal | 967 kJ |
| Salmon fillet (grilled) | 154 g | 280 kcal | 1,171 kJ |
| Whole milk (1 cup / 244 mL) | 244 mL | 149 kcal | 623 kJ |
| Cola (355 mL can) | 355 mL | 140 kcal | 586 kJ |
| Black coffee | 240 mL | 2 kcal | 8 kJ |
| Butter (1 tablespoon) | 14 g | 102 kcal | 427 kJ |
| Chocolate bar (milk, standard) | 44 g | 235 kcal | 983 kJ |
| Big Mac (McDonald's, approximate) | 220 g | 563 kcal | 2,355 kJ |
Daily energy intake reference
The World Health Organization (WHO) and most national dietary guidelines express recommended daily energy intake in both kcal and kJ:
| Group | Daily intake (kcal) | Daily intake (kJ) |
|---|---|---|
| Children 2–3 years | 1,000–1,400 kcal | 4,184–5,858 kJ |
| Children 4–8 years | 1,200–1,600 kcal | 5,021–6,694 kJ |
| Adolescents 9–13 years | 1,400–2,200 kcal | 5,858–9,205 kJ |
| Adult women (sedentary) | 1,600–2,000 kcal | 6,694–8,368 kJ |
| Adult women (active) | 2,000–2,400 kcal | 8,368–10,042 kJ |
| Adult men (sedentary) | 2,000–2,600 kcal | 8,368–10,878 kJ |
| Adult men (active) | 2,400–3,000 kcal | 10,042–12,552 kJ |
| Standard food label reference | 2,000 kcal | 8,368 kJ |
Exercise energy burn (kcal and kJ)
These estimates are for a 70 kg (154 lb) adult. Energy burn scales with body weight — a 90 kg person burns roughly 30% more.
| Activity | Duration | kcal burned | kJ burned |
|---|---|---|---|
| Walking (5 km/h) | 30 min | ~140 kcal | ~586 kJ |
| Jogging (8 km/h) | 30 min | ~280 kcal | ~1,171 kJ |
| Running (12 km/h) | 30 min | ~400 kcal | ~1,674 kJ |
| Cycling (moderate) | 30 min | ~240 kcal | ~1,004 kJ |
| Swimming (moderate) | 30 min | ~250 kcal | ~1,046 kJ |
| Weightlifting | 30 min | ~180 kcal | ~753 kJ |
| Yoga | 60 min | ~200 kcal | ~837 kJ |
| HIIT | 30 min | ~350 kcal | ~1,464 kJ |
Calories to kJ conversion table
| Calories (kcal) | Kilojoules (kJ) | Calories (kcal) | Kilojoules (kJ) |
|---|---|---|---|
| 50 kcal | 209.2 kJ | 600 kcal | 2,510.4 kJ |
| 100 kcal | 418.4 kJ | 700 kcal | 2,928.8 kJ |
| 150 kcal | 627.6 kJ | 800 kcal | 3,347.2 kJ |
| 200 kcal | 836.8 kJ | 900 kcal | 3,765.6 kJ |
| 250 kcal | 1,046.0 kJ | 1,000 kcal | 4,184.0 kJ |
| 300 kcal | 1,255.2 kJ | 1,200 kcal | 5,020.8 kJ |
| 350 kcal | 1,464.4 kJ | 1,500 kcal | 6,276.0 kJ |
| 400 kcal | 1,673.6 kJ | 1,800 kcal | 7,531.2 kJ |
| 450 kcal | 1,882.8 kJ | 2,000 kcal | 8,368.0 kJ |
| 500 kcal | 2,092.0 kJ | 2,500 kcal | 10,460.0 kJ |
| 550 kcal | 2,301.2 kJ | 3,000 kcal | 12,552.0 kJ |
Frequently asked questions
Is 1 calorie the same as 1 kcal?
On food labels, yes — "Calories" (with a capital C) always means kilocalories (kcal). Scientifically, 1 calorie (lowercase) = 0.001 kcal. So a 200-Calorie snack = 200 kcal = 836.8 kJ. To avoid confusion, most health professionals use "kcal" for food energy and reserve "calorie" for scientific contexts.
How many kJ is 2,000 calories?
2,000 kcal × 4.184 = 8,368 kJ. This is the reference daily intake used on nutrition labels in the US (2,000 Calories) and Australia/NZ (8,700 kJ, slightly rounded up). If your label says "based on a 8,700 kJ daily diet," that's approximately 2,079 kcal.
Why do Australian food labels show kJ but US labels show Calories?
It's a historical difference in measurement systems. Australia adopted SI units (metric, including joules) in 1974; the US retained the non-metric calorie convention. Both values represent the same energy — just measured in different units. A product with "630 kJ" in Australia has "150 Cal" in the US.
What is the difference between kJ and kcal?
Both measure energy. 1 kcal = 4.184 kJ exactly. "kJ" (kilojoule) is the SI unit of energy; "kcal" (kilocalorie) is the traditional dietary unit. Kilojoules are used by scientists and in metric countries; kilocalories dominate in the US, Canada, and UK nutrition labeling. Nutritionally, they're interchangeable — just different scales.
How do I convert kJ back to calories?
Divide kJ by 4.184 to get kcal (food calories). So 2,092 kJ ÷ 4.184 = 500 kcal. See our kJ to calories converter for the reverse calculation with a full table and food label examples.
How many kJ is 500 calories?
500 kcal × 4.184 = 2,092 kJ. This is roughly the energy in a standard restaurant starter or a small fast-food meal. It also represents about a 25% reduction from a 2,000 kcal/day reference diet — often cited in weight loss contexts as a daily deficit target.
Sources and references
- Food and Agriculture Organization (FAO) / WHO. Energy and protein requirements. WHO Technical Report Series, No. 724.
- U.S. Department of Agriculture (USDA). FoodData Central. National Agricultural Library.
- Food Standards Australia New Zealand (FSANZ). Energy calculation for food labels. FSANZ, 2020.
- Bureau International des Poids et Mesures (BIPM). The International System of Units (SI), 9th edition, 2019. (Definition of joule.)
- Ainsworth BE et al. 2011 Compendium of Physical Activities. Medicine & Science in Sports & Exercise, 2011.
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