its different for everyone.
first you figure up Basal Metabolic Rate (there's calculators for this)
then you multiply that by your 'activity level'. since people stuck at a desk job like me burn fewer calories than construction workers, that activity multiplier ranges from 1.1 to 1.6
the final number is a rough estimate of your maintenance calories for a day. if you're blessed with a fast metabolism, the calories are even higher. if you damaged your metabolism with bad crash diets/starvation, or have thyroid problems, total calories are lower.
