BMR stands for Basal Metabolic Rate - the number of calories your body uses to perform basic life-sustaining functions while at rest.
Mifflin St Jeor Equation
$$\text{BMR} = 10 \times \text{Weight (kg)} + 6.25 \times \text{Height (cm)} - 5 \times \text{Age (years)} + \text{Sex Constant}$$
- Sex Constant: +5 for men, -161 for women
Example for a Female
- Weight: 150 lbs (68 kg)
- Height: 65 inches (165 cm)
- Age: 30 years
$$\text{BMR} = 10 \times 68 + 6.25 \times 165 - 5 \times 30 - 161$$
$$\text{BMR} = 680 + 1031.25 - 150 - 161 = 1400.25 \text{ calories/day}$$