NEW AND ABIT CONFUSED! :S

im reeeeely sorry if this has been answered before but..

to calculate your daily requirements are you supposed to calculate your calorie intake for a sendentary lifestyle as well as adding in the calories you burn through activities and exercise each day? 

so for example:

my BMR is calculated somewhere at at = 1,283

Sedentary Lifestyle Assumption e.g. light walking on the job, light housekeeping, deskwork, running errands, etc: 1,283 multiplied by 1.2 = 1,540

calories burned through excercise each day varies for me. so for example say i burned 400 calories today, would i then need to add this number to my sedentary lifestyle needs of 1,540?  which would then add up to 1,940.

so 1,940 would roughly be the amount i would need for this day? (taking into account that calculations will change as calories burned will vary)

am i right or am i just talking total nonsense?

oh and another question.. (sorryyy)

say i ate 1,800 for the day and only burned 100 (1,800 eaten - 100 burned = 1,700 for the day) does that now mean i have gone over my minimum of 1,540 and would start to gain weight if continued eating above that number?

argh.. my heads spinning!

your responce would greatly be appreciated :]

Your BMR is the amount of calories that your body burns just being alive with no additional exercise. You're right. Any additional exercise would be added to that.  Say for example that your BMR is 1500 and you do an hour of circuit training burning 400.  That day your body would have burnt 1900 calories.  So, if you are trying to lose weight you want to burn more than you consume.  If you are trying to maintain your weight you need to burn about the same amount that you consume.  To gain weight you need to consume more than you burn.

Hope that helps. 

All of these numbers are just intended to give you a very general idea. But the numbers are just theory, your reality might be different.  People of exact same stats can have widely different RMRs... hundreds above or below this number. But further, I just read a study that said that the BMR numbers (basically same thing) is about 12% higher than when people were actually tested. This site says I need about 1700 to maintain... but I eat more like 1550 to maintain.

Also on this site, if I add up all the activity I do, and what I supposedly burn, I come up with a number more like 2200.

The reason why you are confused, is that the method you are doing is confusing... and furthermore may be way different that your reality.

There are only three pieces of information you know with any degree of certaintly.

1) How many calories you eat on average
2) How many hours a week of exercise you do.
3) What the scale says.

So pick a calorie level, and then see what the scale says. Keep good records. Make adjustments if needed.

ok so my BMR is calculated somewhere around 1,200.. this is the minimum i must eat which my body NEEDS  n order for my body to function properly, yeah i know.. 

assuming that everyone is sedentary in their everyday life i calculated my sedentary lifestyle to be 1,500 which is the number i must go by to maintain my weight at 98 lbs, right?

but is my BMR of 1,200 already included in the calculation of my sedentary lifestyle needs or do i need to add tese two together? =S

It's already included.  You don't need to add them.