Calorie calculator. Gives a safe and healthy estimate of how many calories you really need. Stop starving yourselves out there! Low calorie diets can have many other long-term negative internal side effects to your organs and systems.
You always think you need to eat fewer calories, and exercise. In reality, you need to net at least 1200 calories to function. That means, if you're burning 300 calories, you need to ADD 300 calories to your diet in a healthy way to keep going.
From Susan Powter's StoP the INsAniTY Website. I know, she's gone a little off the deep end, but back in the day, she was the fitness lo-fat guru. The chart comes from the mayo clinic. You can trust it.