kJ to kcal Converter

Convert kilojoules (kJ) to kilocalories (kcal, "大卡") for food nutrition, diet planning, and fitness tracking. 1 kilocalorie = 4.184 kilojoules (exact conversion factor).

Core Conversion:

1 Kilocalorie (kcal) = 4.184 Kilojoules (kJ) | 1 Kilojoule (kJ) ≈ 0.239 kcal

kcal = kJ ÷ 4.184 | kJ = kcal × 4.184 (e.g., 100 kJ ≈ 23.9 kcal; 500 kcal ≈ 2092 kJ)

kJ

Accepts decimals (e.g., 1000 kJ ≈ 239.01 kcal)

kcal

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Quick conversions (common food energy) - click to auto-fill:

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About kJ and kcal

Key differences between kilojoules (kJ) and kilocalories (kcal) — and when to use each

kJ vs kcal Comparison

Unit Definition Common Uses Global Adoption
Kilojoule (kJ) 1 kJ = energy to move 1 kg 1 meter with 1 newton force (SI unit) Food nutrition labels (most countries), science, engineering Global standard (EU, Asia, Australia, Canada)
Kilocalorie (kcal) 1 kcal = energy to heat 1 kg water by 1°C (food "calorie") Food labels (US), diet planning, fitness tracking ("大卡") Primary in US; secondary in most other countries

Kilojoule (kJ)

  • International System of Units (SI) for energy — scientific standard
  • 1 kJ = 1000 joules (J); 1 megajoule (MJ) = 1000 kJ
  • Used on food labels in 90% of countries (EU, Japan, Brazil)
  • Directly convertible to other energy units (e.g., 1 kJ ≈ 0.278 Wh)

Kilocalorie (kcal)

  • Commonly called "calorie" in food contexts (1 kcal = 1 "food calorie")
  • 1 kcal = 1000 "small calories" (cal) — historical energy unit
  • Primary unit for diet apps (MyFitnessPal) and US food labels
  • Intuitive for daily use (e.g., average adult needs ~2000 kcal/day)

Common Food Energy (kJ & kcal)

Food Item (1 serving) Kilojoules (kJ) Kilocalories (kcal) Notes
Apple (medium, ~150g) 418 kJ 100 kcal Fresh, unpeeled
White rice (cooked, ~150g) 1000 kJ 239 kcal Long-grain
Hard-boiled egg (1 piece) 167 kJ 40 kcal Medium-sized (~50g)
Cheeseburger (fast-food) 2092 kJ 500 kcal With beef patty & cheese
Coca-Cola (330ml can) 564 kJ 135 kcal Regular (not diet)

kJ to kcal Conversion Table

Common energy conversions for food, diet, and fitness

Kilojoules (kJ) Kilocalories (kcal) Use Case
100 kJ 23.90 kcal 1 small banana
500 kJ 119.50 kcal 1 slice of bread + 1 tbsp peanut butter
1000 kJ 239.01 kcal 1 bowl of oatmeal + milk
2000 kJ 478.02 kcal 1 serving of grilled chicken salad
4184 kJ = 1000.00 kcal 1 large meal (e.g., steak + potatoes)

Conversion factor: 1 kcal = 4.184 kJ (exact). All values rounded to 2 decimal places for practical use.

Frequently Asked Questions

Common questions about kJ to kcal conversions

Why do food labels show both kJ and kcal?

Dual labeling accommodates global standards and consumer habits:

  • kJ: Required by international food regulations (EU, Codex Alimentarius) as the SI unit.
  • kcal: Familiar to consumers in the US and many countries for diet tracking (e.g., "2000 calorie diet").
  • Practicality: Helps travelers, expats, and global brands avoid confusion across markets.
How do I convert kJ to kcal (and vice versa)?

Use the exact conversion factor 1 kcal = 4.184 kJ:

kcal = kJ ÷ 4.184

kJ = kcal × 4.184

Example 1: Convert 500 kJ to kcal

500 kJ ÷ 4.184 ≈ 119.50 kcal

Example 2: Convert 300 kcal to kJ

300 kcal × 4.184 = 1255.2 kJ

Is "calorie" on food labels the same as kcal?

Yes! The "calorie" you see on food labels is actually a kilocalorie (kcal):

  • 1 "food calorie" = 1 kcal = 1000 "small calories" (the scientific "cal" unit).
  • This naming shortcut started in the early 1900s to avoid confusing consumers with large numbers (e.g., "100 kcal" is easier than "100,000 cal").
  • To confirm: Check the label for "kcal" (most US labels) or "kJ" (global labels) — if it says "cal," it’s always kcal.
How accurate do I need to be when converting for diet tracking?

For most people, rounding to 1-2 decimal places is enough:

  • Everyday use: Round to 1 decimal place (e.g., 100 kJ ≈ 23.9 kcal → 24 kcal) — the difference is negligible for daily intake.
  • Precise tracking: Use 2 decimal places (e.g., 100 kJ ≈ 23.90 kcal) — helpful for strict diets or fitness goals.
  • Food labels: Manufacturers often round values to whole numbers (e.g., 418 kJ → 100 kcal) — you don’t need more precision than the label.
Why is the conversion factor 4.184?

The 4.184 factor comes from the definition of a kilocalorie:

  • 1 kcal is defined as the energy needed to heat 1 kilogram of water from 14.5°C to 15.5°C at standard atmospheric pressure.
  • Scientists measured this energy in joules (the SI unit) and found it equals 4184 joules (J).
  • Since 1 kilojoule = 1000 joules, 4184 J = 4.184 kJ — hence 1 kcal = 4.184 kJ.

This is an exact scientific standard, so the conversion factor never changes.

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