I always squawk on calories in and calories out. In fact, I probably speak of it at least 3-4x/wk! I have inserted a graph from the MayoClinic to simplify things. Remember that you have calories already stored as fat, your body needs X amount of calories to help you function through your day, and then you add on what you don't need!
"Moderate aerobic exercise includes such activities as brisk walking, swimming and mowing the lawn. Vigorous aerobic exercise includes such activities as running and aerobic dancing. Strength training can include use of weight machines, or activities such as rock climbing or heavy gardening."
"As a general goal, aim for at least 30 minutes of physical activity every day. This chart shows the estimated number of calories burned while doing various exercises for one hour. Specific calorie expenditures vary widely depending on the exercise, intensity level and your individual situation."