cal

You've probably heard about counting calories when talking about food and exercise. A cal—short for calorie—is a unit of energy! It measures how much energy your body gets from the food you eat or how much energy you burn during activity. Think of it like fuel—everything needs some to run! While often associated with diets, cals are used in science too, measuring energy in chemical reactions and other processes. So next time you're enjoying a snack, remember you're taking in cals that power your day.

The term "cal" (short for calorie) is a unit of energy—specifically the amount of heat needed to raise the temperature of one gram of water by one degree Celsius. While many people think of calories mostly in relation to food, the unit is also a core concept in physics and chemistry.

Originally, scientists used cals to measure the heat of fuels and chemical reactions—often by literally burning substances and measuring the heat released. Today, when you see “calories” on food packaging, those numbers are usually kilocalories (kcal), meaning 1,000 calories. That is why nutrition labels and nutritionists often use “Calorie” with a capital C to mean a kilocalorie instead of a small calorie.

Beyond food, cals are used in many scientific fields, helping us understand energy transfer in everything from engines to biological processes. For example, your body burns cals through exercise and even while resting; the more active you are, the more you burn.

So while a cal might look like just a number on a label, it's actually a powerful unit for making sense of energy in all its forms—from fueling our bodies to powering the world around us.