kilocalorie (dietary) (kcal)
1 kilocalorie (dietary) = 4,184 joules
What is kilocalorie (dietary)?
A kilocalorie, written as Calorie with a capital C in nutrition contexts, is a unit of energy equal to 1,000 thermochemical calories. It is the standard unit used to express the energy content of food on nutrition labels globally.
Notes: Food calorie
Real-world uses
Kilocalories are the standard unit for food energy labelling in the United States (labelled as "Calories" with a capital C), dietary planning, and exercise energy expenditure. A typical adult needs about 2,000 kcal/day. Fitness trackers report calories burned in kcal.
History
Wilbur Atwater pioneered the use of kilocalories for food energy measurement in the 1890s. The confusing convention of using a capital-C "Calorie" to mean kilocalorie originated in American nutritional science and persists on US food labels today.
Common mistakes
The most common mistake is confusing Calories (kcal) with calories (cal)—they differ by a factor of 1,000. When food labels say "100 Calories," they mean 100 kilocalories. Also, assuming all macronutrients have the same caloric density (fat has 9 kcal/g vs 4 kcal/g for protein and carbohydrates).
When is this conversion used?
Electricity bills use kilowatt-hours while physics calculations use joules. Converting between them is essential for energy audits, comparing appliance efficiency, and understanding power consumption. Nutritional information is labelled in kilocalories in some countries and kilojoules in others, making this conversion important for dietary planning and food science.
How to convert kilocalorie (dietary) to joule
To convert kilocalorie (dietary) to joule, multiply the value by 4,184.
Conversion formula (from base unit)
x * 4184.0
Measurement standards
The joule is the SI derived unit of energy, defined as one kilogram-metre-squared per second-squared (kg·m²/s²). The kilowatt-hour, equal to exactly 3.6 megajoules, is accepted for use with the SI by the BIPM for practical electricity metering.
Did you know?
A single bolt of lightning releases roughly 1 to 5 gigajoules of energy, yet only a small fraction reaches the ground as electrical current. Most of the energy dissipates as light, heat, and the thunder shockwave.
| kilocalories (dietary) | joules |
|---|---|
| 0.1 | 418.4 |
| 0.5 | 2,092 |
| 1 | 4,184 |
| 2 | 8,368 |
| 5 | 20,920 |
| 10 | 41,840 |
| 25 | 104,600 |
| 50 | 209,200 |
| 100 | 418,400 |
| 250 | 1,046,000 |
| 500 | 2,092,000 |
| 1,000 | 4,184,000 |
Common values
| kilocalories (dietary) | joules | |
|---|---|---|
| A food calorie (1 kcal) | 1 kilocalorie (dietary) | 4,184 joules |
| A AA battery | 2.23709369 kilocalories (dietary) | 9,360 joules |
| Boiling a kettle | 100.38240918 kilocalories (dietary) | 420,000 joules |
| Daily human diet (2000 kcal) | 2,000 kilocalories (dietary) | 8,368,000 joules |
| 1 gallon of gasoline | 31,491.3957935 kilocalories (dietary) | 131,760,000 joules |
Full kilocalorie (dietary) conversion table
| Unit | Value | Factor |
|---|---|---|
| joule | 1 kcal = 4,184 J | × 4,184 |
| kilojoule | 1 kcal = 4.184 kJ | × 4.184 |
| kilowatt hour | 1 kcal = 0.00116222 kWh | × 0.00116222 |
| calorie (thermochemical) | 1 kcal = 1,000 cal | × 1,000 |
| watt hour | 1 kcal = 1.16222222 Wh | × 1.16222222 |
| megajoule | 1 kcal = 0.004184 MJ | × 0.004184 |
| electronvolt | 1 kcal = 2.611447e+22 eV | × 2.611447e+22 |
| British thermal unit | 1 kcal = 3.96566683 BTU | × 3.96566683 |
| therm (US) | 1 kcal = 0.00003967 therm | × 0.00003967 |