I need to add a cautionary note to the above post. Formulas like Harris-Benedict and others have the advantage of looking and sounding scientific and reliable. But many of us here at 3FC have found them to be wildly inaccurate. Personally, I don’t pay much attention to them except to say – I wish it were so!
Harris-Benedict gives my BMR as 1326 (and Schofield as 1400). Based on the fact that I exercise 6 – 7 days a week for an average of 90 minutes, plus work as a personal trainer, I picked the ‘very active’ multiplier (hard exercise/sports 6-7 days/week) though I think I might even qualify for 'extra active' (very hard daily exercise/sports & physical job or 2X day training). The result is that I should theoretically be able to maintain my weight at 2287 calories.

Unfortunately, that many calories spells certain and quick weight gain for me. In order to get my actual highest maintenance calories (1600), I’d have to use the ‘sedentary’ multiplier, though I don’t think that ‘sedentary’ is a particularly accurate description of my lifestyle.
It can be fun to play around with numbers for calories burned and metabolic rates, but be aware that all these calculators are guesstimates. In my experience working with overweight women, the numbers given are often way too HIGH. It can be frustrating for our members to calculate out the perfect number for weight loss, only to have it not work.
My alternative suggestion is to honestly track calories – weighing and measuring and journaling every bite, lick, and taste – to see how YOUR unique body reacts to a particular calorie level. This way you can tweak and devise your own personal diet plan that works for YOU.