1) Your age 
2) Your Gender
3) your activity level 
Calculate how often you exercise and use this BMR
MEN: 66+(6.23* weight in pounds) +(12.7* height in inches) - (6.76* age in years) 
WOMEN: 655+ (4.35* weight in pounds ) + (4.7* height in inches) - (4.7* age in years)
 I Hope this helps ;)