Enter kilocalories or watt-hours into the calculator to convert to the other value, with support for kcal, Cal, cal, kJ, J, Wh, kWh, and BTU.
- All Unit Converters
- Kcal to kW Conversion Calculator
- Cal to kWh Conversion Calculator
- kJ to Calories Calculator
- BTU to Calories Conversion Calculator
- Cal to BTU Conversion Calculator
Kcal to Wh Conversion Formula
The calculator uses two formulas, one for each mode.
Energy mode (kcal to Wh):
Wh = kcal × 4184 / 3600 = kcal × 1.162222
Rate mode (kcal/hour to W):
W = (kcal/hour × 4184) / 3600 = kcal/hour × 1.162222
- Wh = energy in watt-hours
- W = power in watts
- kcal = kilocalorie, also called food Calorie (Cal with a capital C)
- 4184 = joules in one kilocalorie (thermochemical kcal)
- 3600 = seconds in one hour, used to convert joules to watt-hours
The factor 1.162222 Wh per kcal is exact under the thermochemical definition of the calorie. The international table calorie gives 1 kcal = 4186.8 J, which rounds to the same 1.163 Wh per kcal at typical precision. The calculator assumes input values are non-negative. Energy is conserved in the conversion, so no efficiency or loss factor is applied. If you need the electrical energy a device actually delivers, multiply the result by the device efficiency.
The kcal to Wh tab converts a fixed energy amount. Enter kcal, cal, kJ, or J and the calculator first converts to joules, then divides by 3600 to get Wh. The kcal/hour to W tab converts an energy rate to continuous power. It applies the same joule conversion, then divides by 3600 seconds per hour to give watts. One kcal per hour equals 1.162222 watts because a watt is defined as one joule per second.
Reference Tables
Common kcal values converted to Wh:
| Energy (kcal) | Energy (Wh) | Energy (kJ) |
|---|---|---|
| 1 | 1.162 | 4.184 |
| 10 | 11.62 | 41.84 |
| 100 | 116.2 | 418.4 |
| 250 | 290.6 | 1,046 |
| 500 | 581.1 | 2,092 |
| 1,000 | 1,162 | 4,184 |
| 2,000 | 2,324 | 8,368 |
Typical kcal/hour rates and their watt equivalents:
| Activity or source | kcal/hour | Watts |
|---|---|---|
| Resting adult (BMR) | 70 | 81 |
| Walking (3 mph) | 240 | 279 |
| Cycling (moderate) | 500 | 581 |
| Running (6 mph) | 700 | 814 |
| Trained cyclist (sustained) | 860 | 1,000 |
Examples and FAQ
Example 1. A meal contains 600 food Calories. How much energy is that in watt-hours?
Wh = 600 × 1.162222 = 697.3 Wh, or about 0.70 kWh. That is roughly the energy a 100 W bulb uses in 7 hours.
Example 2. A cyclist burns 450 kcal in one hour. What is the average power output in watts?
W = 450 × 1.162222 = 523 W. Note that this is metabolic power. Mechanical power at the pedals is lower because human muscle efficiency is around 20 to 25 percent, giving roughly 105 to 130 W of useful output.
Why is 1 kcal not exactly 1 Wh? The kilocalorie and the watt-hour come from different definitions. A kcal is defined by heat (joules), and a Wh is defined by power times time. The fixed ratio between joules and seconds gives the 1.162 conversion factor.
Is a food Calorie the same as a kcal? Yes. The Calorie with a capital C used on nutrition labels equals one kilocalorie, or 1,000 small calories.
Can I use this for battery sizing? The result is the raw energy. Real batteries lose energy to heat, charge controllers, and inverters. Multiply the Wh result by your system efficiency, often 0.80 to 0.90, to estimate usable output.
What is the difference between Wh and W? Wh is energy, the total amount used or stored. W is power, the rate of use. Energy equals power multiplied by time, so 100 W running for 1 hour equals 100 Wh.
