21 kcal is equal to 21000 cal.
The conversion from kilocalories (kcal) to calories (cal) involves multiplying the kcal value by 1000, because 1 kcal equals 1000 cal. Hence, 21 kcal multiplied by 1000 results in 21000 cal.
Conversion Tool
Result in cal:
Conversion Formula
The formula to convert kilocalories (kcal) to calories (cal) is simple: multiply the kcal value by 1000. This works because one kcal equals exactly one thousand calories. The calorie (cal) is a unit of energy, and kilocalorie (kcal) is just a larger unit, one thousand times bigger.
Mathematically:
cal = kcal × 1000
For example, to convert 21 kcal to cal:
- Start with 21 kcal
- Multiply 21 by 1000
- 21 × 1000 = 21000 cal
This step-by-step shows that 21 kcal contains 21000 calories.
Conversion Example
- Convert 5 kcal to cal:
- Take 5 kcal
- Multiply by 1000
- 5 × 1000 = 5000 cal
- Convert 0.75 kcal to cal:
- Start with 0.75 kcal
- 0.75 × 1000 = 750 cal
- Convert 12.3 kcal to cal:
- Take 12.3 kcal
- Multiply 12.3 by 1000
- 12.3 × 1000 = 12300 cal
- Convert 100 kcal to cal:
- 100 kcal multiplied by 1000
- 100 × 1000 = 100000 cal
- Convert 0 kcal to cal:
- 0 × 1000 = 0 cal
Conversion Chart
| kcal | cal |
|---|---|
| -4.0 | -4000 |
| -3.0 | -3000 |
| -2.0 | -2000 |
| -1.0 | -1000 |
| 0.0 | 0 |
| 1.0 | 1000 |
| 2.0 | 2000 |
| 3.0 | 3000 |
| 4.0 | 4000 |
| 5.0 | 5000 |
| 10.0 | 10000 |
| 15.0 | 15000 |
| 20.0 | 20000 |
| 25.0 | 25000 |
| 30.0 | 30000 |
| 35.0 | 35000 |
| 40.0 | 40000 |
| 45.0 | 45000 |
| 46.0 | 46000 |
The chart shows kcal values in the left column and their equivalent cal values on the right. To find the calorie amount for any kcal, simply look up the kcal in the left column then read the converted value across. Negative kcal values represent negative energy values, which may be used in some scientific contexts.
Related Conversion Questions
- How many calories are in 21 kilocalories?
- What is 21 kcal converted to calories exactly?
- Is 21 kcal equal to 21000 cal or another value?
- How do I convert 21 kcal to cal manually?
- What formula do I use to change 21 kcal into calories?
- Can 21 kcal be expressed in calories and how much is it?
- Are kcal and cal the same unit when converting 21 kcal?
Conversion Definitions
kcal: Kilocalorie, often called a large calorie, is a unit of energy representing 1000 small calories. It’s commonly used to measure the energy content in food and in nutrition. One kcal equals the energy needed to raise the temperature of one kilogram of water by one degree Celsius.
cal: The calorie is a unit of energy, originally defined as the amount of heat necessary to raise the temperature of one gram of water by one degree Celsius. It is smaller than kilocalorie, and often used in physics and chemistry, although food energy is mostly given in kilocalories.
Conversion FAQs
Why multiply kcal by 1000 to get calories?
Because the kilocalorie (kcal) is exactly 1000 times bigger than the calorie (cal). So to convert kcal to cal, you multiply by 1000. This is a standard metric conversion between kilo- (1000 times a unit) and the smaller unit. It ensures the energy value stays accurate across units.
Can kcal values be negative like in the chart?
Negative kcal values can appear in scientific calculations or thermodynamics, representing energy loss or consumption. In regular nutrition, negative kcal is rare or doesn’t make practical sense. But mathematically, the conversion applies the same way, so you can convert negatives to calories by multiplying by 1000.
Is cal still used in nutrition or only kcal?
Nutrition labels and food energy use kilocalories (kcal) almost exclusively to avoid confusion, because calories (cal) are much smaller. Using cal would give very large numbers. However, in physics and chemistry, cal remains a valid energy unit for precise measurements.
Does the conversion change with the temperature or pressure?
No, the conversion between kcal and cal is fixed and does not depend on temperature or pressure. These units measure energy quantities, so their relationship is constant by definition regardless of environmental conditions.
How precise is the factor 1000 in kcal to cal conversion?
The factor 1000 is exact by definition. One kilocalorie equals exactly 1000 small calories. This precision comes from the metric prefix kilo- which means 1000, so there’s no approximation involved in the conversion.