BMR = basal metabolic rate. This is the rate at which your body burns calories while lying quietly at rest (in the morning, on waking), 8-12 hours after eating (post-absorptive state).
If is a measure of your bodies requirements were you to stay that way all day and is to do with the requirements of your organs, .
You then have to add in:
N.E.A.T = Non-exercise accociated thermogenesis. This is the energy required for you to do every day things such as walking, talking, cooking, cleaning, showering, washing, working etc etc... This is actually a BIG CHUNK of a persons energy requirements and is usually the reason why there are those people who are 'endlessly eating but really skinny' people - they are genetically programmed to 'move more'.
E.A.T = Exercise accociated thermogenesis. This is the energy required for your body to do specific exercise (eg: weight training, track, cardio).
T.E.F = Thermogenic effect of food. This is the energy required to digest, absorb and utilise the energy in your foods. It is variable depending on your diet (more protein and fibre increases this, more fats and sugars decreases it).
There is no easy way to calculate these - and most of the online calculators and equations are wrong.
Your better off picking a non-stupid calorie level and sticking to that intake for a few weeks whilst monitoring your in the mirror, then simply adjust as required.