Basal Metabolic Rate (BMR) is the number of calories your body burns doing absolutely nothing. It's the single largest component of your daily energy expenditure and the starting point for any nutrition plan.
The formulas
Mifflin–St Jeor (men) = 10×weight(kg) + 6.25×height(cm) − 5×age + 5; women subtract 161 instead of adding 5. Katch–McArdle = 370 + 21.6×lean-body-mass(kg), which accounts for body composition directly.
From BMR to daily calories
BMR alone won't tell you how much to eat. Multiply it by an activity factor to get your TDEE, then adjust up or down for your goal.
Frequently asked questions
BMR is what you burn at complete rest. TDEE is your total daily burn — BMR plus digestion, daily movement and exercise. TDEE = BMR × an activity factor.
Mifflin–St Jeor is the best-validated for the general population. If you know your body-fat percentage, Katch–McArdle can be more accurate because it's based on lean mass.
Occasionally and briefly, but it's rarely necessary. Creating your deficit from TDEE instead keeps intake higher, protects muscle and is easier to sustain.