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 ;)