Calorie requirements vary from person to person. Of course it depends on weight/height, metabolic rate, activity level, goals, etc. If you are training hard and most days of the week (5+) then you might need more calories to prevent loss of too much weight. I for example want to build more muscle and shed the little bit of fat around it. I am quite small (5'4, 112 lbs.) and average around 1850-2000 calories a day, working out 5-6 days/wk. I used to do around 1600 but I was getting too thin. I have noticed that a lot of fitness/workout programs recommend around 1300-1500 calories for toning and defining muscle but I have found this to be unrealistic because I lost quite a lot of weight that way. Those recommendations are good for people who have a weight loss/shredding goal. I have also tried some different "calorie counters" tools but the recommendations they've given have not worked for me--again being way too low. Just remember that the most important thing about calories is the quality of them. You don't want too much sugar or empty carbs or processed/packaged foods (especially being careful to minimize these towards the evening). Really though, it takes time to figure out your body so just experiment with different portions, foods, and adding/subtracting calories here and there until you find your balance. Good luck!