Convert energy units — joules, calories, kilowatt-hours, BTU, kilojoules.
| Unit | Name | Value |
|---|---|---|
| J | Joule | 4.184 |
| kJ | Kilojoule | 0.004184 |
| kcal | Kilocalorie (Cal) | 0.001 |
| kWh | Kilowatt-hour | 0.0000011622222 |
| BTU | BTU | 0.0039656512 |
Formula: Kilocalorie = Calorie × 0.001
Multiply any calorie value by 0.001 to get kilocalorie.
Reverse: Calorie = Kilocalorie × 1000
Common calorie values — factor: 1 cal = 0.001 kcal
| Calorie (cal) | Kilocalorie (kcal) | Context |
|---|---|---|
| 1 cal | 0.001 kcal | 1 cal |
| 5 cal | 0.005 kcal | 5 cal |
| 10 cal | 0.01 kcal | Small candy |
| 50 cal | 0.05 kcal | 50 cal |
| 100 cal | 0.1 kcal | Short walk |
| 500 cal | 0.5 kcal | Snack |
| 1,000 cal | 1 kcal | Light meal |
| 5,000 cal | 5 kcal | Meal |
| 1e+04 cal | 10 kcal | Large meal |
| 5e+04 cal | 50 kcal | Daily intake fraction |
| 1e+05 cal | 100 kcal | 100 kcal |
| 5e+05 cal | 500 kcal | 500 kcal workout |
| 1e+06 cal | 1,000 kcal | 1 Mcal |
| 1.000e+09 cal | 1e+06 kcal | 1 Gcal |
| 1.000e+12 cal | 1.000e+09 kcal | 1 Tcal |
1 cal = 0.001 kcal. Memorize for instant estimates.
Use 0.001 as a quick mental multiplier.
Multiply result by 1000 to recover the original cal value.
Prescribes daily energy intake and food portion sizes in kcal.
Calculates calorie burn during workouts and links to dietary targets.
Measures energy content of food products for nutritional labeling.
Creates weight management plans based on daily kcal targets.
Optimizes pre/during/post workout nutrition using kcal calculations.
Calculates nutritional information per serving in kcal for labels.
The calorie (cal) was defined in 1824 as the heat needed to raise 1 gram of water by 1°C. There are two versions: the small calorie (cal = 4.184 J) and the large calorie or kilocalorie (kcal = 4,184 J), which is the 'Calorie' used in nutrition.
The calorie remains standard in chemistry for heat of reaction measurements. In the US, food packaging uses 'Calories' (with capital C) which are actually kilocalories — a persistent source of confusion.
Interesting fact: The confusion between cal and kcal means that a food label saying '200 Calories' actually means 200 kcal = 200,000 cal = 836,800 joules. The SI unit for food energy is the kilojoule.
The kilocalorie (kcal) equals 1,000 calories or 4,184 joules, and is the unit used on food labels worldwide (often written as 'Cal' with a capital C in the US). It was standardized by the International Table calorie in 1956.
Nutritionists, dietitians, and food scientists use kcal for daily energy intake recommendations. Most adults need 2,000–2,500 kcal/day. Exercise apps, fitness trackers, and dietary plans all operate on kcal.
Interesting fact: One gram of fat yields about 9 kcal, one gram of carbohydrate or protein yields about 4 kcal. A single sugar cube (4g) contains about 16 kcal.
Converting calorie to kilocalorie is common across energy, nutrition, engineering, and science. Different sectors use different energy units — joules in physics, kcal in nutrition, kWh in electricity, and BTU in HVAC — making accurate conversion essential for cross-disciplinary work and international comparisons.
Quick reference: 5 cal = 0.005 kcal and 10 cal = 0.01 kcal. Reverse: 1 kcal = 1000 cal. Exact factor: 1 cal = 0.001 kcal.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.