Basal Metabolic Rate, I like to think of it as Basis Metabolic Rate, is the number of calories you'd burn if you stayed in bed all day, if you were in a coma.
This is the Formula:
Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )
Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in year )
But since I am no good with working it I search BMR calculator and use one of those.