Convert watts to calories per second, or to kcal over a set time, and calories back to watts, with an optional cycling estimate of food Calories burned.
Watts to Calories Formula
The formula below describes direct energy conversion, not human calorie expenditure. The thermochemical calorie is exactly 4.184 J; 1 food Calorie (kcal) is 1,000 cal or 4,184 J. The displayed multiplier 0.239005736 is rounded; the calculator divides by 4.184 directly. See NIST conversion factors.
Variables:
- C = calories (cal)
- W = power in watts
- s = time in seconds
Watts measure how quickly energy is transferred. Average watts multiplied by seconds gives joules. In cycling mode, metabolic joules = measured mechanical watts times seconds divided by gross efficiency; reverse mechanical watts = entered metabolic joules times gross efficiency divided by seconds. The editable 23% default is an illustration, not a measured or universal efficiency. Gross efficiency includes baseline metabolism, so do not add resting energy again. Gross and delta efficiency are distinct measures.
Quick Conversion Facts
- 1 watt for 1 second = 0.2390 cal
- 100 watts for 60 seconds = 1,434.03 cal = 1.4340 kcal
- 250 watts for 10 minutes = 35,850.86 cal = 35.8509 kcal
- 500 watts for 5 minutes = 35,850.86 cal = 35.8509 kcal
- 1,000 watts for 60 seconds = 14,340.34 cal = 14.3403 kcal
Common Watts to Calories Conversions
| Power (W) | Time | Calories (cal) | Food Calories (kcal) |
|---|---|---|---|
| 50 | 60 s | 717.02 | 0.7170 |
| 100 | 60 s | 1,434.03 | 1.4340 |
| 250 | 60 s | 3,585.09 | 3.5851 |
| 100 | 300 s | 7,170.17 | 7.1702 |
| 250 | 300 s | 17,925.43 | 17.9254 |
| 500 | 300 s | 35,850.86 | 35.8509 |
| 100 | 600 s | 14,340.34 | 14.3403 |
| 250 | 600 s | 35,850.86 | 35.8509 |
| 500 | 600 s | 71,701.72 | 71.7017 |
| kcal values are food calories. | |||
How to Calculate Calories from Watts
- Enter the power in watts.
- Enter the duration and select minutes, seconds or hours beside the field. Choose direct conversion or the cycling estimate. For the reverse solve, enter calorie energy instead of power.
- Multiply watts by time to get total energy, then convert that result into calories.
- Select Calculate or press Enter. Read both calorie units, joules, watt-hours and calorie rate. In cycling mode, open the optional panel to review or change the assumed gross efficiency; watt-hours describe mechanical output work.
Example Calculation
If power is 200 watts and time is 90 seconds:
That equals 4,302.10 cal, or 4.3021 kcal.
