I used the bmr last year when i was dieting
I got the formula on the internet and calculated it myself (didn use web calculator) and deducted 500cals per lb a wk i wanted to lose (max deduction 1000)
I also had an app on my ipod that was like a food diary and it used the brm method aswell.. It gave me a very similar calorie allowance with a varying of ten cals at max... Ended up losing 20lbs (fell off the wagon when visiting m8s and only back on it now)
Id recommend using it but calculate ur own bmr and compare it to a web calc to be sure... If u want i can post ur bmr?!
EDIT:
I decided to calculate it anyway 
Men: BMR = 66 + ( 6.23 x weight lbs ) + ( 12.7 x height inches ) - ( 6.8 x age yrs )
--> results from online calc-->2089.47
-->results from formula calc-->2021.89 (keep in mind hadn got a calculator so this may be a lil off)
"To determine your total daily calorie needs, multiply your BMR by the appropriate activity factor, as follows:
If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2
If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375
If you are moderatetely active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55
If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725
If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9"