RDI Basal Metabolic Rate (BMR) = 655 + (4.354 x weight in pounds) + (4.569 x height in inches) + (4.7 x age in years)

For example, a woman weighs 150 lbs, stands 5'6" and is 28 years old.
Her BMR would be:

BMR = 655 + (4.354 x 150) + (4.569 x 66) + (4.7 x 28)
BMR = 655 + 653.1 + 301.6 + 131.6
BMR = 1741 kCals per day