For educational purposes only. Not personalised health advice. This calculator has not been reviewed by a registered dietitian, physician or exercise physiologist. Results are population estimates and can be wrong for you individually. Speak to a qualified professional before acting on them, particularly if you are pregnant, under 18, managing a medical condition, or have a history of disordered eating.
BMR Calculator
Your Basal Metabolic Rate (BMR) is the number of calories your body needs each day simply to stay alive at complete rest. It accounts for the energy used by your heart, lungs, kidneys, brain, and every other organ working continuously in the background. BMR does not include any physical activity. The Mifflin-St Jeor equation, developed in 1990 and validated across multiple populations, is the standard formula recommended by the Academy of Nutrition and Dietetics for estimating BMR in healthy adults. It uses your weight, height, age, and biological sex to produce a calories-per-day figure. Your Total Daily Energy Expenditure (TDEE) takes that number further by multiplying your BMR by an activity factor ranging from sedentary (desk job, little exercise) to very active (hard training twice a day). TDEE is the calorie level at which your weight stays the same. Eating below TDEE creates a deficit for weight loss; eating above it creates a surplus for muscle gain. Enter your details below to see your BMR and TDEE across five activity levels.
Formula
Male: BMR = 10 * weight(kg) + 6.25 * height(cm) - 5 * age + 5
Female: BMR = 10 * weight(kg) + 6.25 * height(cm) - 5 * age - 161
TDEE = BMR * activity factor
Sedentary: 1.2 | Light: 1.375 | Moderate: 1.55 | Active: 1.725 | Very active: 1.9
Turning BMR into a daily calorie target
Your basal metabolic rate is the energy your body burns at complete rest, keeping your heart, brain, kidneys and cells running. It is not what you can eat. To reach a maintenance figure you multiply BMR by an activity factor, roughly 1.2 for a desk-bound day, up to about 1.9 for hard physical labour or heavy training. That multiplier, not the BMR itself, is where most people miscalculate, because almost everyone overestimates how active they actually are.
Once you have maintenance calories, a change of weight is a change of energy balance. A deficit of about 500 calories a day is the common target for losing roughly one pound a week, but the popular 3,500 calories per pound rule is only an approximation: as you lose weight your BMR falls with your body mass, so the same deficit slows over time and plateaus are normal, not failure.
Two practical cautions. Aggressive deficits below your BMR are counterproductive for most people, costing muscle and depressing metabolism. And formulas such as Mifflin-St Jeor estimate an average body; they cannot know your individual muscle mass or thyroid function, so treat the number as a two-week experiment to adjust from, not a fixed rule.
BMR Calculator: frequently asked questions
What is BMR?
Basal Metabolic Rate is the number of calories your body burns at complete rest to maintain basic physiological functions such as breathing, circulation, and cell production. It represents your minimum daily energy requirement.
Which BMR formula is most accurate?
The Mifflin-St Jeor equation, used here, is widely regarded as the most accurate for most adults. A 2005 study published in the Journal of the American Dietetic Association found it predicted resting energy expenditure within 10% for the majority of participants.
What is TDEE?
Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor. It represents the total calories you burn in a day accounting for exercise and movement. Eating at your TDEE maintains your current weight.
How do I use BMR to lose weight?
Eat below your TDEE to create a calorie deficit. A deficit of 500 calories per day produces roughly 0.45 kg (1 lb) of weight loss per week. Do not eat below your BMR without medical supervision, as this can deprive your body of essential energy.
Does BMR change over time?
Yes. BMR decreases with age as muscle mass naturally declines. It also changes with significant weight gain or loss, muscle building, illness, and hormonal changes. Recalculate your BMR every few months or after major body composition changes.
Official sources
- Mifflin MD, et al. (1990). "A new predictive equation for resting energy expenditure in healthy individuals." American Journal of Clinical Nutrition, 51(2):241-247.
- CDC: Balancing Calories
This content is provided for educational purposes only and has not been reviewed by a qualified specialist in this field. See our methodology.