Calorie vs. kilocalorie

The so called 'small calorie' is the energy needed to increase the temperature of 1 gram of water from 14 °C to 15 °C.

The 'large calorie' is the energy needed to increase the temperature of 1 kilogrma of water from 14 °C to 15 °C. This is exactly 1000 small calories.

In nutrition, they used large calories but write them with tha capital C - not calories but Calories, meaning 1000 small calories. For example, 1 gram of sugar has about 3.95 kilocalories but on the labels, you'll see 3.95 Cal.

1 Joule is approximately 0.239 small calories.