The amount of energy, or calories, you need in a day depends on several factors including your basal metabolic rate (BMR) and the types of activities and exercise you do.

Your BMR is the energy your body needs at rest. In other words, it is the energy used by your body to perform basic bodily functions such as breathing, keeping the heart beating, and maintaining body temperature. In addition to the calories burned at rest, your body burns calories as it performs activities. The number of calories used depends on your weight, the type of activity, and the intensity at which you are doing the activity.

To estimate the amount of energy you use up in a day, enter your age, gender, height and weight. Then, estimate the number of hours or minutes you spend doing activities for each of the five intensity levels. You'll see how your activities and exercise affect your total energy requirements.