Calorie Converter: kcal to kJ & MET-Based Calorie Burn
Whether you're comparing international nutrition labels or estimating how many calories you burn during exercise, understanding the relationship between kcal, kJ, and metabolic equivalents (METs) gives you the precision to plan smarter.
Calories, Kilocalories, and Kilojoules
The small calorie (cal) is the energy needed to raise 1 gram of water by 1°C. In nutrition and fitness, the unit that matters is the kilocalorie (kcal) — equal to 1,000 small calories. When a food label says "200 Calories," it means 200 kcal. The capital-C Calorie (Cal) and kcal are identical.
Internationally, energy is also expressed in kilojoules (kJ). One kcal equals exactly 4.184 kJ. Australian and European food labels show both units, so converting between them is a routine task for anyone tracking nutrition across borders.
MET Values and Calorie Burn
The Metabolic Equivalent of Task (MET) quantifies how intense an activity is relative to sitting quietly (MET = 1.0). An activity with MET = 9.8 burns 9.8 times as many calories per unit time as rest. The formula is simple:
Calories burned (kcal) = MET × body weight (kg) × time (hours)
MET values are published by the Compendium of Physical Activities and are widely used by exercise scientists, trainers, and wearable fitness devices to estimate energy expenditure.
Key Formulas
- kcal = kJ ÷ 4.184
- kJ = kcal × 4.184
- Calories burned (kcal) = MET × weight (kg) × time (hr)
kcal to kJ Quick Reference
| kcal | kJ |
|---|---|
| 100 | 418 |
| 200 | 837 |
| 500 | 2,092 |
| 800 | 3,347 |
| 1,200 | 5,021 |
| 1,600 | 6,694 |
| 2,000 | 8,368 |
| 2,500 | 10,460 |
| 3,000 | 12,552 |
MET Values for Common Activities
| Activity | MET Value | kcal/hr (70 kg person) |
|---|---|---|
| Walking (3.5 mph) | 3.5 | 245 |
| Running (6 mph) | 9.8 | 686 |
| Cycling (moderate) | 8.0 | 560 |
| Swimming laps | 8.0 | 560 |
| Yoga | 3.0 | 210 |
| HIIT | 12.0 | 840 |
| Weight training | 5.0 | 350 |
| Rowing machine | 8.5 | 595 |
kcal/hr calculated as MET × 70 kg. Adjust proportionally for your body weight.
Frequently Asked Questions
What is the difference between a calorie and a kilocalorie?
A small calorie (cal) is the energy needed to raise 1 gram of water by 1°C. A kilocalorie (kcal) equals 1,000 small calories and is the unit used in food labeling and nutrition. When people say "calories" in everyday language — as in "200 calories in an apple" — they actually mean kilocalories (kcal). The dietary Calorie (written with a capital C) is identical to one kilocalorie.
How do I convert kcal to kJ?
Multiply kilocalories by 4.184 to get kilojoules. For example, 500 kcal × 4.184 = 2,092 kJ. To convert kJ back to kcal, divide by 4.184. International food labels (Australia, the EU, and others) display energy in both kcal and kJ, so this conversion is frequently needed when reading imported nutrition labels.
How many calories does running burn per hour?
Calories burned while running depend on your body weight and pace. Using the MET formula (Calories/hr = MET × body weight in kg), running at 6 mph has a MET of 9.8. A 70 kg person burns approximately 9.8 × 70 = 686 kcal per hour. A 90 kg person burns about 882 kcal per hour at the same pace. Faster paces have higher MET values and burn more calories.