What is a Calorie?

When we refer to a calorie, we genuinely mean 1000 calories (a kcal).

One calorie is the amount of energy it takes to raise one gram of fluid one degree higher.A kcal is the amount of energy it takes to raise 1 kg one degree higher.

Therefore when you look at nutrition labels, it will always use an uppercase C to specify it's a kcal.

Outside Northern America, they use joules to measure the energy in food. 1 kcal =4.18 joules.