How many watts in a calorie?

Answer 1

calories and watts cannot be converted.

A calorie is a measurement of energy. A watt is a measurement of power. It would be like asking "What is 1000 gallons of gas in miles per hour?" When you buy electricity you buy energy (not power) units called kilowatt-hours. Do not confuse this with kilowatts per hour. Spend some time thinking about power, energy, rate and force. They can be very confusing and are often misused so look for what the author meant to say.

The simple answer is 1 calorie = .001162 watt hours.

1 nutritional calorie (1000 calories (go figure)) = 1.1620 watt hours.

1000 (nutritional) calories (kCal) = 1162 watt-hours.

The inefficient body the conversion is about 20%.

Therefore 1000 kCal =1162 watt-hours * .20 = 232 watts-hour work output.

Detailed

• Calories can be converted into watt-minutes, watt-hours, watt-days and other units of energy.
• A calorie is a unit of energy and applies to anything that contains energy, including food. The nutritional Calorie, which this question is about, is 1000 science calories or one kCal.
• If you were to consume the recommended 2500 kCal a day, you would be using as much energy as a 120w light bulb being lit for one day or 120 watt-days or 2880 watt-hours.

I have a crank generator that has a 100 watt light bulb connected to it. When I am cranking fast enough to get the bulb to full brightness I am putting 100 watts into the bulb. If I do it for one minute I have put 20% or 1.4 kCal into the bulb and 4.6 kCal into making me me very hot. I am burning a total of 6 kCal each minute. This can vary wildly depending on the type of exercise, body weight, room temperature, etc.

From

http://www.livestrong.com/thedailyplate/fitness/exercise/bicycling-stationary-moderate-150-watts/

Calories on a 150 watt bicycle machine for a 145 lb person

• "609 Calories/hour" = 150 watt-hours work output
• 609 kCal = 1.162 * 609 watt-hours = 707 watt-hours
• This body is 21% efficient.

Answer 2

1 cal = 4.186 Joules

1 watt = 1 Joule/1sec

keep in mind that food calories (Cal) are really kilocalories (kcal)