How many joules are in one kilocalorie?

One kilocalorie (kcal) equals exactly 4,184 joules (J) using the thermochemical definition. Equivalently, 1 kcal = 4.184 kilojoules (kJ) or 0.004184 megajoules (MJ).

Is a "food Calorie" the same as a kilocalorie?

Yes. The "Calorie" printed on nutrition labels (with a capital C) is a kilocalorie (kcal) — 1,000 small thermochemical calories. When a food item says 200 Calories, it means 200 kcal or 836,800 J.

Why do some countries show kJ instead of kcal on food labels?

EU regulations require both kJ and kcal on food packaging. The kilojoule is the SI unit of energy, so it is more consistent with scientific standards, while kcal persists for historical familiarity.

What is the difference between the thermochemical calorie and the International Table calorie?

The thermochemical calorie (cal_th) is exactly 4.184 J; the International Table calorie (cal_IT) is 4.1868 J — a 0.07% difference. Nutrition and most everyday contexts use the thermochemical definition, which this tool applies.

How do I convert megajoules to kcal?

Multiply megajoules by 1,000,000, then divide by 4,184. For example, 1 MJ = 1,000,000 / 4,184 ≈ 239.0 kcal. You can also select "MJ" in this tool and enter your value directly.

Joules to Kilocalories Converter

Convert joules (J), kilojoules (kJ), or megajoules (MJ) to kilocalories (kcal) and back, with a food and exercise reference table.

Energy Converter

Input unit

J kJ MJ

Value

kcal

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Food & Exercise Reference

Food / Serving	kcal	kJ

Activity (30 min, 70 kg)	kcal burned	kJ burned

Joules (J)	kcal	Kilojoules (kJ)	kcal

1 kcal = 4,184 J = 4.184 kJ = 0.004184 MJ • 1 kJ ≈ 0.239006 kcal • Thermochemical definition

Summary

This tool converts energy values between joules (J), kilojoules (kJ), megajoules (MJ) and kilocalories (kcal — the "food Calories" shown on nutrition labels). One kilocalorie equals exactly 4,184 joules (thermochemical definition), so 1 kJ is approximately 0.239006 kcal. The bidirectional converter handles all three SI prefixes on the joule side, and the reference table below puts common food and exercise values in context.

How it works

Choose your input unit: J, kJ, or MJ.
Type an energy value into the input field.
The converter instantly shows the result in kcal and the equivalent in both the other SI energy units.
Use the swap button to reverse the direction (kcal to J/kJ/MJ).
Scroll to the reference table for common food and exercise energy values.

Use cases

Translate nutrition-label kilojoules into kilocalories when reading EU food packaging.
Convert physics homework answers between SI joules and food-energy kilocalories.
Estimate how many kilojoules of exercise offset a specific food item.
Cross-check calorimeter measurements against joule equivalents in thermodynamics coursework.
Convert MJ energy readings from industrial or solar applications to kcal for reporting.
Verify fitness tracker data that mixes kJ and kcal across platforms.

Frequently Asked Questions

Last updated: 2026-06-19 · Reviewed by Nham Vu