Calories

What Kimny said and really it depends mostly on your height, gender, and amount of body fat. Since your metabolism is a biological function, it will ebb and flow every day depending on many factors. Your ability to follow a calorie deficit depends on stress, health, and so many factors that it's not really a formula, it's a guideline and it will require some trial and error, careful recording, and paying attention to how you feel. Be patient and you will succeed! Best of luck to you! -Roberta