A calorie is the amount of energy that is supplied in the nutrients that make up food. Because it is a form of energy, calories can be converted to joules through a measurement of heat.
Calories in nutrition measure the amount of energy needed to heat 1 kg of water 1 degree Celsius. When finding calories in food, scientists will break down the food to its basic form, place it in a metal container and then submerge the container in water. They will then measure the initial temperature of the water, ignite the food and then measure the temperature difference afterword in Celsius. The amount of calories is found in a formula where calories equals the mass of the water multiplied by the specific heat of water and multiply that by the change in temperature. The greater the change in temperature, the more calories in the food.
The joule is a metric unit of measurement equal to one newton, which is equal to kilograms multiplied by meters per second squared. A newton is a measurement equaling the force of energy necessary to accelerate a 1 kg object 1 meter/second. Joules are a form of kinetic energy, and as a form of kinetic energy can be converted to calories.
Calories in One Joule
A standard conversion in the Systeme Internation de'Unites is that one calorie equals 4.186 joules, which is how much energy is given off in heat to raise 1 kg of water 1 degree Celsius. Because heat is a form of energy, it can be converted to joules. If 4.186 calories are in one joule, then 0.2389 calories are in one joule. To find calories per joule, divide calories by joules: 1/4.186=0.2389 cal/joule. Because 4.186 joules is equal to one calorie, this is the number of calories in one joule.